JAMB UTME - Physics - 2024

Answer Details

To calculate the energy consumption of an appliance, you can use the formula:

Energy (in KWh) = Power (in kW) × Time (in hours)

First, convert the power rating of the refrigerator from watts (W) to kilowatts (kW). Since 1 kW is equal to 1000 W, you can convert 150W to kilowatts by dividing by 1000:

150 W = 0.150 kW

Next, calculate the energy consumed over the period the refrigerator is kept on, which is 336 hours. Use the formula:

Energy = 0.150 kW × 336 hours

Now, perform the multiplication:

Energy = 50.40 kWh

Therefore, when the refrigerator is kept on for 336 hours non-stop, it consumes 50.40 kWh of energy. This is the correct choice.

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To find the density of the fluid, we need to apply the principle of floatation, which states that the weight of the fluid displaced by the submerged part of the object is equal to the weight of the object. Let's walk through the steps:

Step 1: Understand the volume submerged

The hydrometer has a total volume of 2y x 10^-5 m³. It floats with 20% of its volume above the fluid. Hence, 80% of its volume is submerged in the fluid.

Submerged Volume, V_sub = (0.80) x (2y x 10^-5 m³) = 1.6y x 10^-5 m³

Step 2: Apply the principle of floatation

The weight of the fluid displaced equals the weight of the hydrometer.

Weight of hydrometer = Mass x Gravity = y kg x g (where g is the acceleration due to gravity). For the purpose of calculations, g can be considered as 9.81 m/s².

Weight of displaced fluid = Density of fluid (ρ_fluid) x Submerged Volume x g

According to the principle of floatation:

y x g = ρ_fluid x 1.6y x 10^-5 m³ x g

g is common on both sides and can be canceled out:

y = ρ_fluid x 1.6y x 10^-5

Step 3: Solving for the density of the fluid

ρ_fluid = y / (1.6y x 10^-5)

The y on both numerator and denominator cancels out:

ρ_fluid = 1 / (1.6 x 10^-5)

ρ_fluid = 6.25 x 10⁴ kg/m³

Thus, the density of the fluid is 6.25 x 10⁴ kg/m³.

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The mouthpart adapted for piercing and sucking is found in the mosquito. Mosquitoes have a specialized mouth structure called a proboscis. This proboscis is long and slender, allowing mosquitoes to puncture the skin of their hosts and suck blood. The proboscis is a complex structure that contains several needle-like parts that make the piercing and sucking process efficient and effective.

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The force of attraction between molecules of the same substance is called cohesion.

To understand this simply:

Cohesion refers to the attractive forces acting between similar molecules. For example, water molecules attract each other due to hydrogen bonding, which is a strong intermolecular force.

Let's break down some important concepts:

• Cohesion: This force is responsible for phenomena like water forming droplets and the surface tension that allows some insects to walk on water.
• Capillarity: This is not related to cohesion directly, but rather to the movement of liquid within narrow spaces without the assistance of external forces, usually due to a combination of cohesion and adhesion.
• Adhesion: This is the force of attraction between unlike molecules, such as water sticking to the surface of a glass.
• Surface Tension: While related to cohesion, this specifically refers to the effect caused by cohesive forces at the surface of a liquid, which makes the surface act like a stretched elastic membrane.

In summary, **cohesion** is the force that keeps the molecules of the same substance, like water, attracting each other.

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When the thermal energy in a solid is increased, the solid particles gain energy and begin to vibrate more vigorously. As the temperature rises, these particles eventually have enough energy to overcome the forces holding them in their fixed positions. This leads to a change of state from a solid to a liquid. This process is known as melting.



To further understand this, imagine an ice cube. As it absorbs heat, it gains energy, and the ice (which is a solid) starts to turn into water (which is a liquid). This transition is what we refer to as melting.



Thus, the term that describes this change of state, when a solid is heated and turns into a liquid, is melting.

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When a body moves in a straight line from one point, such as point P, to another point, such as point Q, the motion is called Translational Motion. This kind of motion refers to an object moving along a path in which every part of the object takes the same path as a reference point. This means that if you follow any point on the body, it covers the same amount of distance in the same time frame as any other point.

Let's break down the other options:

• Rotational Motion: This occurs when an object spins around an internal axis. For example, the rotation of the Earth on its axis is a rotational motion.


• Simple Harmonic Motion: This is a type of periodic motion where the restoring force is directly proportional to the displacement. An example of this is a pendulum swinging back and forth.


• Circular Motion: This occurs when an object moves along a circular path. For instance, the motion of the planets around the sun is circular motion.

In conclusion, since the body is moving from point P to point Q along a straight line, it exhibits Translational Motion.

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To understand which of these gas laws is equivalent to work done, we must first understand the basic concept of work in the context of gases. For gases, work is done when there is a change in volume under pressure, typically expressed as W = P ΔV, where W is work, P is pressure, and ΔV is the change in volume.

Let's consider the given gas laws:

• Charle's law states that the volume of a gas is directly proportional to its temperature at constant pressure.
• Pressure law (often referred to as Gay-Lussac's law) says that the pressure of a gas is directly proportional to its temperature at constant volume.
• Boyle's law states that the pressure of a gas is inversely proportional to its volume at constant temperature. In equation form, this is P₁V₁ = P₂V₂.
• Gay-Lussac's law is another name for the Pressure law.

Among these, Boyle's law relates directly to work done because it involves a change in volume at constant temperature, implying that work occurs as a gas expands or compresses. The equation P₁V₁ = P₂V₂ is foundational for calculating work done in reversible processes, which aligns with the expression for work done on a gas, W = P ΔV. Thus, **Boyle's law** is most directly connected to the concept of work done on a gas.

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In this problem, the tension in the rope results in a force that acts to pull the body along the horizontal surface. The rope is inclined at 30º to the vertical, which means it makes an angle of 60º with the horizontal since the total angle between vertical and horizontal is 90º.

To find the tension in the rope, we first understand that the component of the tension force acting along the horizontal surface is given by the formula:

F_horizontal = Tension * cos(θ)

Where:

• F_horizontal is the effective force pulling the body along the horizontal, given as 15N.
• Tension is the total tension in the rope that we need to find.
• θ is the angle of inclination with respect to horizontal = 60º (since the rope is 30º to the vertical, it's 60º to the horizontal).

Given that F_horizontal = 15N, we substitute into the equation:

15N = Tension * cos(60º)

We know that cos(60º) = 0.5, therefore:

15N = Tension * 0.5

To find the Tension, divide both sides of the equation by 0.5:

Tension = 15N / 0.5

Tension = 30N

Therefore, the tension in the rope is 30N.

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The main feature of trees in the savanna habitat is the possession of thick, corky bark. The savanna is characterized by a distinct wet and dry season. During the dry season, fires are common as dry grasses and leaves become highly flammable. To adapt to this environmental condition, many trees in the savanna have developed a thick, corky bark which helps protect them against these frequent fires. This bark acts as an insulator, shielding the vital inner tissues of the tree from the heat of the flames. Additionally, this adaptation helps the trees retain moisture, which is crucial during the arid months when water is scarce.

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Inbreeding is the process where closely related individuals, like cousins or siblings, mate and produce offspring. **This practice is highly discouraged in humans for several reasons, but a significant concern is the potential for an outbreak of hereditary diseases.**

Here’s why inbreeding is problematic:

• Humans carry genes in pairs, and some of these genes might be recessive, meaning they only show their effects if an individual inherits two copies of the same gene (one from each parent). These genes might cause diseases or other health issues.
• When two closely related individuals mate, the chance of both carrying the same recessive genes is **higher**. This increases the likelihood that their offspring will inherit these genes, leading to hereditary diseases. **This genetic similarity can result in a higher risk of disorders such as cystic fibrosis, sickle cell anemia, and Tay-Sachs disease**.
• While some may argue that inbreeding could lead to other issues, such as dwarfism or higher death rates in newborns, the primary scientific concern backed by genetics is the increased susceptibility to hereditary diseases.

Therefore, **to promote genetic diversity and reduce the risk of hereditary diseases in offspring, inbreeding is discouraged in human populations**. This way, offspring are less likely to inherit harmful genetic combinations that can lead to health problems.

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To solve the problem, let's first understand the concept of efficiency in this context. Efficiency refers to the ratio of the useful power output to the total power output of a system. In simpler terms, it tells us how much of the power provided by the cell is being effectively used by the resistor, X.

Given that the cell has an internal resistance (r) of 2Ω and we need the efficiency to be 75%, we will follow these steps:

• The total resistance in the circuit is the sum of the internal resistance and the resistance of the resistor X, so it is (r + X).
• Efficiency is given by the formula:

Efficiency (%) = (R / (R + r)) * 100

Where:

• R is the resistance of resistor X.
• r is the internal resistance of the cell.

According to the problem, efficiency is 75%, so:

(X / (X + 2)) * 100 = 75

First, let’s eliminate the percentage by dividing both sides by 100:

(X / (X + 2)) = 0.75

Now, let's solve for X:

1. Multiply both sides by (X + 2):

X = 0.75 * (X + 2)



2. Distribute the 0.75:

X = 0.75X + 1.5



3. Subtract 0.75X from both sides:

0.25X = 1.5



4. Finally, divide by 0.25:

X = 1.5 / 0.25



5. Solve for X:

X = 6 Ω

Hence, for the cell to have an efficiency of 75%, the value of the resistor X must be 6Ω.

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To find the area expansivity of a metal when given its cubic expansivity, you should understand the relationship between linear, area, and cubic expansivity.

Cubic expansivity (\( \beta \)) is defined as the fractional change in volume per change in temperature, and is given by the formula:

\[ \Delta V = \beta V \Delta T \]

Area expansivity (\( \alpha_{A} \)) corresponds to the fractional change in area per change in temperature and can be derived from the linear expansivity (\( \alpha \)). The relationship between these expansivities is as follows:

\[ \text{Area Expansivity (\( \alpha_{A} \))} = 2 \times \text{Linear Expansivity (\( \alpha \))} \]

The cubic expansivity (\( \beta \)) is related to the linear expansivity by:

\[ \text{Cubic Expansivity (\( \beta \))} = 3 \times \text{Linear Expansivity (\( \alpha \))} \]

Thus, based on these relationships, we can express the area expansivity in terms of the cubic expansivity:

\(\text{Area Expansivity (\( \alpha_{A} \))} = \frac{2}{3} \times \text{Cubic Expansivity (\( \beta \))}

Given that the cubic expansivity \( \beta \) is \( 3.9 \times 10^{-6} \, \text{K}^{-1} \):

The area expansivity can be calculated as follows:

\[ \text{Area Expansivity (\( \alpha_{A} \))} = \frac{2}{3} \times 3.9 \times 10^{-6} \, \text{K}^{-1} = 2.6 \times 10^{-6} \, \text{K}^{-1} \]

Therefore, the **correct answer** is **2.6 x 10^{-6} K^{-1}**.

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To calculate the quantity of heat absorbed or released by a substance, we can use the formula:

Q = C × ΔT

where:

• Q is the quantity of heat.
• C is the thermal capacity of the substance.
• ΔT is the change in temperature.

Given:

• C = 400 J/°C
• Initial temperature = 60°C
• Final temperature = 80°C

First, calculate the change in temperature:

ΔT = Final temperature - Initial temperature = 80°C - 60°C = 20°C

Now, substitute the values into the formula to find the quantity of heat:

Q = 400 J/°C × 20°C

Calculate the answer:

Q = 8000 J

Since the options provided are in kilojoules (KJ), we need to convert joules (J) to kilojoules (1 KJ = 1000 J):

Q = 8000 J ÷ 1000 = 8 KJ

Therefore, the quantity of heat for the copper rod, given the specified conditions, is 8 KJ.

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A non-rechargeable cell, commonly known as a primary cell, is a type of chemical battery that is designed to be used once until the chemical reactions that produce electricity are exhausted. After this point, the cell cannot be reversed or recharged.

In the given examples, the dry leclanche cell is a well-known example of a non-rechargeable cell. It is commonly used in everyday devices like remote controls, wall clocks, and torches. This cell type utilizes zinc and manganese dioxide as electrodes and relies on a moist paste of ammonium chloride for the electrolyte.

The other examples, such as nickel iron, mercury cadmium, and lead-acid, involve rechargeable cells (secondary cells) that are specifically designed to endure multiple charges and discharges throughout their useful life. Thus, unlike the dry leclanche cell, these can be recharged after use.

Therefore, the dry leclanche cell is an ideal example of a non-rechargeable cell because it can only be used once. After depletion, it cannot be recharged or reused.

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To calculate the power of an object, we need to use the formula for power in terms of work done over time. The formula is:

Power (P) = Work Done (W) / Time (t)

First, let's find the work done on the object. Work done can be calculated using the formula:

Work Done (W) = Force (F) × Distance (d)

Given:

• Force (F) = 50 N
• Distance (d) = 500 cm = 5 m (Note: We need to convert the distance from centimeters to meters because the unit of force is in newtons, and 1 m = 100 cm)

Substituting the values into the formula for work done, we get:

Work Done (W) = 50 N × 5 m = 250 Joules

Next, we consider the time it took for the object to move this distance:

• Time (t) = 1 s

Now, substituting the work done and time into the power formula:

Power (P) = 250 Joules / 1 s = 250 Watts

Thus, the power of the object is 250 Watts.

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When investigating electrolysis, the most relevant instrument from the list provided is the Voltameter. This is because the voltameter is specifically designed to measure the amount of substance that is deposited or consumed at electrodes during the electrolysis of an electrolyte. It functions based on the chemical change associated with the electric current passing through the electrolyte.

Here is a simple explanation of how electrolysis works and why a voltameter is useful:

Electrolysis is the process of using electricity to cause a chemical reaction, which is usually a decomposition reaction. This involves passing an electric current through an electrolyte (a substance containing free ions). These ions migrate towards electrodes, resulting in chemical changes. The key aspect to measure during electrolysis is the amount of material (e.g., metal or gas) that is deposited at the electrodes.

The Voltameter helps in understanding electrolysis because:

• It can measure the amount of electrons passing through the circuit, which relates directly to the mass of substances transformed at the electrodes according to Faraday's laws of electrolysis. These laws state that the amount of chemical change is proportional to the quantity of electricity passed.
• By measuring the quantity of the substance deposited, one can gain insights into the efficiency of the electrolytic process and how different variables (such as voltage and current) affect the process.

Voltmeter, Ammeter, and Galvanometer are not used primarily for investigating electrolysis:

• A Voltmeter measures electrical potential difference between two points in an electric circuit, which is useful for understanding voltage but not directly for measuring chemical changes in electrolysis.
• An Ammeter measures the current flowing through a circuit and provides information about the electrical aspects of the process but not the chemical changes.
• A Galvanometer detects and measures small electric currents, and while sometimes used to detect current flow, it is not specifically designed for measuring outcomes of electrolysis.

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The energy in a moving car is an example of kinetic energy.

To explain simply, **energy** is the ability to do **work** or cause **change**. There are different forms of energy, and **kinetic energy** is one of them. It is defined as the energy possessed by an object due to its motion.

When a car is moving, it possesses **kinetic energy** because its components are in **motion**. This motion energy allows the car to do tasks, such as transporting people or goods from one place to another. The faster the car moves, the greater its **kinetic energy**, and thus it can make a larger impact or do more work.

In contrast, energy forms like **mechanical energy** is a combination of both kinetic and potential energy; **electrical energy** is associated with electrical charge movement, while **potential energy** is related to the position or condition of an object (like a car parked on a hill). Therefore, the specific type of energy from a moving car is **kinetic energy**.

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According to the kinetic theory of gases, the pressure exerted by a gas on the walls of its container relates to the behavior and movement of its molecules. To understand how this pressure forms, let's explore the following essential concepts.

Molecules in a gas move rapidly and randomly in all directions. When these molecules collide with the walls of their container, they exert force due to the change in momentum during these collisions. The frequency and force of these collisions contribute directly to the pressure experienced by the container walls.

The **pressure** exerted by the gas can be described in terms of the rate of change of momentum imparted by the walls per second per unit area. This means that pressure is determined by considering how fast and how much the momentum of the gas molecules changes when they bounce off the container's walls, spread over a specific area and over time. In simpler terms, the faster and more frequently molecules hit the walls, and the higher their change in momentum, the greater the pressure is.

This explanation can be directly associated with the statement: "rate of change of momentum imparted by the walls per second per unit area", which accurately describes the concept of pressure in the context of the kinetic theory of gases.

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To understand when a vapor is considered saturated, it is crucial to consider the rates of two significant processes: evaporation and condensation. **Evaporation** is the process where liquid molecules escape into the vapor phase, and its rate is denoted as **y**. On the other hand, **condensation** is the process where vapor molecules return to the liquid phase, with its rate denoted as **x**.

A vapor is said to be **saturated** when the rate of evaporation of the liquid is equal to the rate of condensation of the vapor. In simpler terms, the number of molecules leaving the liquid to become vapor is exactly equal to the number of molecules returning from the vapor to the liquid.

In mathematical terms, this condition can be described as **x = y**. Under this condition, the system reaches a dynamic equilibrium, and the vapor pressure of the system is at its maximum for the given temperature. At this point, the vapor cannot accommodate any more molecules, and thus, the vapor is in a saturated state.

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The gravitational force between two objects is determined by Newton's Law of Universal Gravitation, which can be expressed by the formula:

F = G * (m1 * m2) / r²

where F is the gravitational force, G is the gravitational constant, m1 and m2 are the masses of the objects, and r is the distance between the centers of the two objects.

In this problem, it is given that the initial gravitational force is 10N. According to the formula, the gravitational force is inversely proportional to the square of the distance between the two objects.

So, if the distance between the objects is halved (i.e., r becomes r/2), then the new gravitational force F' can be calculated based on the relationship:

F' = G * (m1 * m2) / (r/2)² = G * (m1 * m2) / (r²/4) = 4 * (G * m1 * m2 / r²) = 4 * F

Since the initial force F was 10N, the new force F' when the distance is halved is:

F' = 4 * 10 = 40N

Thus, the new value of the gravitational force is 40N.

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In voltage measurement, a **potentiometer is preferred to a voltmeter** primarily because it **consumes negligible current**. Let me explain this in simpler terms:

A **voltmeter** is an instrument used to measure the potential difference (voltage) across two points in an electrical circuit. However, when a voltmeter is connected, it draws a small amount of current from the circuit to make the measurement, which can slightly alter the voltage being measured. This is particularly an issue in high-resistance circuits where even a small current draw can significantly affect the measurement.

On the other hand, a **potentiometer** is a device designed to measure voltage by comparing it with a known reference voltage without drawing current from the circuit under test. It comes into balance at a point where no current flows through it, ensuring that the measurement is not influenced by the potentiometer itself. This makes it a non-invasive method of measuring voltage, which is particularly useful for precise measurements in sensitive circuits.

Here’s a brief explanation about why the other options listed are less relevant:

• A **wider range** is not a definitive advantage of potentiometers over voltmeters, as it depends on the settings and design of the specific instrument.
• **Bulkiness** is not a factor that inherently makes a potentiometer preferable; in fact, it can sometimes be a disadvantage due to space constraints.
• **Faster response** is not typically associated with potentiometers compared to voltmeters, as both can be designed to have quick response times depending on the technology used.

Therefore, the key advantage of the potentiometer is its **ability to measure voltage without altering the circuit**, which stems from its negligible current consumption. This **ensures more accurate and reliable measurements** in many applications.

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To solve this problem, let's first understand how sound works in a closed pipe. A closed pipe has one end closed and another end open. Sound waves inside such a pipe create standing waves, where nodes (points of no movement) and antinodes (points of maximum movement) are formed.

For a closed pipe, the fundamental frequency (also called the first harmonic) has one node at the closed end and one antinode at the open end. The wavelength is four times the length of the pipe.

The overtone sequence for a closed pipe includes only odd harmonics: 1st (fundamental), 3rd, 5th, 7th, etc. The nth overtone is the 2nth + 1 harmonic. The equation for the frequency of a harmonic in a closed pipe is:

f_n = n * f_1, where f_n is the frequency of the nth harmonic and f_1 is the fundamental frequency

In this case, the fourth overtone corresponds to the 9th harmonic because 2 * 4 + 1 = 9. Therefore, we have:

900 Hz = 9 * f_1

To find the fundamental frequency (f_1), we solve for f_1:

f_1 = 900 Hz / 9

f_1 = 100 Hz

Therefore, the fundamental frequency is 100 Hz.

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To solve this problem, we will use Hooke's Law. Hooke's Law states that the force needed to extend or compress a spring by some distance is proportional to that distance. Mathematically, it is represented as:

F = k * x

where:

• F is the force applied to the spring.
• k is the spring constant.
• x is the extension or compression of the spring from its natural length.

Firstly, we need to find the spring constant k. We know that a force of 10N extends the spring by 0.02m. Therefore, using Hooke's Law:

10N = k * 0.02m

From this, we can solve for k:

k = 10N / 0.02m = 500N/m

Now that we have determined the spring constant, let's calculate the extension caused by a force of 40N:

Using Hooke's Law again:

F = k * x

40N = 500N/m * x

Solving for x:

x = 40N / 500N/m = 0.08m

This means that the spring is extended by 0.08m when a force of 40N is applied. Therefore, the length of the spring (natural length plus extension) becomes:

1.00m + 0.08m = 1.08m

Thus, the **length** of the spring when the applied force is 40N is 1.08m.

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To calculate the acceleration of a charge in an electric field, we start by determining the force acting on the charge. The force \( F \) experienced by a charge \( q \) in a uniform electric field \( E \) is given by the equation:

F = q * E

We are given:

• Charge, q = 1.6 x 10^-19 C
• Electric field, E = 1200 V/m

Substituting these values into the equation for force:

F = 1.6 x 10^-19 C * 1200 V/m

This results in:

F = 1.92 x 10^-16 N

Next, we use Newton’s second law of motion to find the acceleration \( a \) of the charge. This law is given as:

F = m * a

Rearranging for \( a \), we have:

a = F / m

We know:

• Force, F = 1.92 x 10^-16 N
• Mass, m = 9.1 x 10^-31 kg

Substituting these values in the equation for acceleration:

a = \(\frac{1.92 x 10^{-16} N}{9.1 x 10^{-31} kg}\)

Calculating the above expression gives:

a ≈ 2.11 x 10¹⁴ ms^-2

Therefore, the acceleration of the charge is approximately 2.11 x 10¹⁴ ms^-2.

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Newton's Law of Cooling states that the rate of heat loss of an object is directly proportional to the difference in temperature between the object and its surroundings, provided that this temperature difference is small.

Therefore, this law is only valid within a small temperature range.

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apacitance in parallel = one at the top + one under = 2C

The two in the middle are in series = C2 $\frac{C}{2}$

The equivalent capacitance of the capacitors in the circuit above = C2 $\frac{C}{2}$ + 2C = 52 $\frac{5}{2}$C

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Given: Ig ${}_g$ = 50mA = 0.05A, I to be measured = 2A, r = 2Ω $\mathrm{\Omega }$, Is ${}_s$ = I - Ig ${}_g$ = 2 - 0.05 = 1.95A

Shunt(R) = IgIs $\frac{I_g}{I_s}$ x r

R =  0.051.95 $\frac{0.05}{1.95}$ x 10 = 0.2564Ω

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To determine the amount of current required, we need to use Faraday's laws of electrolysis. The first law states that the mass of the substance deposited at an electrode is directly proportional to the quantity of electricity (or charge) that passes through the electrolyte.

Here, we have:

• The mass of the metal deposited, \( m \), is 0.02 kg.
• The electrochemical equivalent, \( z \), is 1.3 x 10^-7 kg/C.
• The time during which the current is applied, \( t \), is 120 seconds.

According to Faraday's first law of electrolysis, the mass (\( m \)) can be calculated by the formula:

m = z \times I \times t

Where:

• m is the mass of the substance deposited (in kilograms).
• z is the electrochemical equivalent (in kg/Coulomb).
• I is the current (in amperes).
• t is the time (in seconds).

Rearranging the formula to solve for current \( I \):

I = \(\frac{m}{z \times t}\)

Substituting the given values into the formula:

I = \(\frac{0.02 \, \text{kg}}{1.3 \times 10^{-7} \, \text{kg/C} \times 120 \, \text{s}}\)

Calculating the denominator:

I = \(\frac{0.02}{1.56 \times 10^{-5}}\)

Solving for \( I \):

I = 1282.05 \, \text{A}

Thus, the appropriate amount of current required to deposit 0.02 kg of metal in 120 seconds is approximately 1.3 x 10³ A.

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The tangential force acting on an object that opposes it from sliding freely on the adjacent surface is called the friction force.

Let me explain each of the options to clarify why friction force is the correct answer:

• Normal force: This is the force exerted by a surface perpendicular (at a right angle) to the object resting on it. It supports the weight of the object, stopping it from passing through the surface. It is not tangential and does not oppose sliding; rather, it acts perpendicular to the surface.
• Friction force: This is the force that acts parallel to the surface contact between two objects or surfaces. It arises when one object tries to move over another. The friction force acts to oppose that movement, providing the necessary resistance to prevent sliding.
• Weight: This is the gravitational force acting downwards due to the mass of an object. It does not act tangentially on the surface but directly downwards towards the center of the Earth.
• Upthrust: Also known as buoyant force, this is the upwards force experienced by an object when it is immersed in a fluid (liquid or gas). It is responsible for the object floating or being pushed up, and is not related to tangential force or friction.

In summary, friction force is the force that acts to oppose sliding between surfaces in contact and acts tangentially, making it the correct answer.

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The diagram is that of the virus. Viruses are obligate parasites, meaning they can't produce their own energy or proteins. They enter the host cell and use the cell's machinery to make their own nucleic acids and proteins. Viruses also use the host cell's lipids and sugar chains to create their membranes and glycoproteins. This parasitic replication can severely damage the host cell, which can lead to disease or cell death. They usually enter your body through your mucous membranes. These include your eyes, nose, mouth, penis, vagina and anus.

Viruses are a unique type of organism that are not plants, animals, or bacteria. They are often classified in their own kingdom. However, for the sake of the question, since most of their attributes and metabolic activities are more of the bacteria, we'll go with option A - Monera

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The phenomenon of land and sea breeze is primarily attributed to convection.

To understand this, let's first look at what land and sea breezes are:

Land Breeze: At night, the land cools down faster than the sea. The cooler, denser air from the land moves towards the sea, and this is known as a land breeze.

Sea Breeze: During the day, the land heats up more quickly than the sea. The warmer, lighter air over the land rises, and the cooler air from the sea moves in to take its place. This movement of air from the sea to the land is known as a sea breeze.

Both of these processes involve the movement of air due to differences in temperature and density, which is essentially the process of convection.

Convection is the transfer of heat through a fluid (like air or water) and is responsible for moving air masses and creating these breezes. The warm air, being less dense, rises, and the cooler, denser air moves in to replace it.

In contrast, conduction is the transfer of heat through a solid material, and radiation is the transfer of heat in the form of electromagnetic waves, neither of which primarily drive the processes of these breezes, making convection the key player.

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The velocity ratio of a machine is a concept used to explain how much the machine is expected to amplify the input motion. If the velocity ratio of a machine is 4, it means that the distance moved by the effort is 4 times greater than the distance moved by the load.

To understand this concept better, consider what a machine does: it allows you to apply a small effort over a longer distance to move a heavy load over a shorter distance. In this scenario, if the velocity ratio is 4, then for every 4 meters (or units of distance) you exert effort, the load will move 1 meter (or unit of distance).

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The defect of the eye lens that occurs when the ciliary muscles are weak is known as Presbyopia.

Here's a simple explanation:

The ciliary muscles in the eye are responsible for helping the lens to change shape so that you can focus on objects at different distances. As people age, the ciliary muscles may become weaker. This weakness hampers their ability to properly adjust the lens. As a result, the lens cannot accommodate or focus as effectively, especially when looking at nearby objects. This leads to a difficulty in seeing objects up close clearly, which is known as presbyopia.

Presbyopia is a natural condition associated with aging, and it typically becomes noticeable in people in their 40s or 50s. This is different from other eye conditions like:

• Myopia, which is when distant objects appear blurry.
• Astigmatism, which is caused by an irregularly shaped cornea leading to blurry or distorted vision at all distances.
• Spherical aberration, which is a concept related to optical systems where light rays striking the edges of a lens do not focus at the same point as light rays passing through the center, but it is not specifically related to the ciliary muscles or biological aging.

So in summary, presbyopia is the condition that results from weakened ciliary muscles, affecting near vision as a person ages.

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The elliptical shape of the Earth: The Earth is not a perfect sphere; it is slightly flattened at the poles and bulging at the equator. This shape causes variations in gravitational acceleration.

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The major building block of an organism is Carbon. Let me explain why in a simple yet comprehensive manner:

Carbon is a unique element found in all living organisms. Its importance comes from its ability to form stable bonds with many other elements, including hydrogen, oxygen, nitrogen, phosphorus, and sulfur. This versatility allows carbon to act as a backbone for the building of complex organic molecules, including proteins, nucleic acids (such as DNA and RNA), carbohydrates, and lipids. These molecules are essential for the structure, function, and regulation of the body's tissues and organs.

Here's why Carbon is indispensable:

• Versatility: Carbon can form four covalent bonds with various atoms, enabling the creation of diverse and complex molecules.
• Formation of Chains and Rings: Carbon atoms can bond with each other to create long chains and rings, serving as the framework for most biomolecules.
• Compound Diversity: Because of its ability to bind with different elements, carbon forms a range of compounds, promoting the complexity and diversity of life.

In summary, Carbon is the primary building block of life due to its unique chemical properties that allow the formation of complex molecules necessary for life's structure and processes.

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The dimension of power in physics is expressed in terms of the base units of mass (M), length (L), and time (T). Power is the rate at which work is done or energy is transferred over time, and it has the unit of watt (W) which is equivalent to one joule per second.

To derive the dimension of power:

1. Work has the dimension of energy, which is force applied over a distance. The dimension of work (or energy) is M L² T^-2 because force has the dimension M L T^-2 and distance adds another L.

2. Since power is work done per unit time, you would divide the dimension of work by time (T).

Thus, the dimensional formula for power is:

M L² T^-3

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The diaphragm in a camera is similar to the iris in the human eye.

Here's a simple explanation:

• Both the diaphragm in a camera and the iris in the eye control the amount of light that enters. The diaphragm adjusts the size of the aperture, which is the opening that allows light to hit the camera's sensor.
• Similarly, the iris adjusts the size of the pupil, which is the opening that allows light to enter the eye and reach the retina.
• The camera's diaphragm is responsible for creating different aperture sizes, just as the iris changes the size of the pupil in different lighting conditions.
• In bright light, both the diaphragm and the iris make their respective openings smaller to reduce the amount of light entering, protecting the camera's sensor and the eye's retina respectively.
• Conversely, in low light conditions, both open wider to allow more light in, enhancing clarity and visibility.

In summary, the iris acts like a natural diaphragm, regulating the light that passes through the eye, much like the diaphragm does in a camera.

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The mass of an object can be calculated using the formula:

Mass = Density × Volume

In this case, we need to find the mass of a solid cube of aluminum. Given:

• Density of aluminum = 2700 kg/m³
• Edge length of the cube = 1.5 cm

First, we need to calculate the volume of the cube. The volume V of a cube with edge length a is given by:

V = a³

Substitute the edge length:

V = (1.5 cm)³ = 1.5 × 1.5 × 1.5 cm³ = 3.375 cm³

Since the density is given in kg/m³, we should convert the volume from cm³ to m³. There are 1,000,000 cm³ in 1 m³, so:

Volume in m³ = 3.375 cm³ × (1 m³/1,000,000 cm³) = 3.375 × 10^-6 m³

Now, use the mass formula:

Mass = Density × Volume

Mass = 2700 kg/m³ × 3.375 × 10^-6 m³

This equals:

Mass = 9.1125 × 10^-3 kg

Convert kg to grams (since 1 kg = 1000 g):

Mass = 9.1125 grams

So, the mass of the cube is approximately 9.1 g. Thus, the correct answer is 9.1 g.

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To calculate the electric field intensity due to a charge, we need to use the formula:

Electric Field Intensity (E) = Force (F) / Charge (q)

In this problem, we are given that the force (F) is 8 Newtons (N) and the charge (q) is 4 microcoulombs (μC). First, we need to convert the charge from microcoulombs to coulombs:

1 microcoulomb (μC) = 1 x 10^-6 coulombs (C)

Therefore, 4 μC = 4 x 10^-6 C.

Now we can use the formula to find the electric field intensity:

E = F / q

E = 8 N / (4 x 10^-6 C)

E = 8 / 4 x 10⁶

E = 2 x 10⁶

Thus, the value of the electric field intensity is 2 x 10⁶ N/C.

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Bilateral symmetry, cylindrical bodies, and double openings are characteristic features of nematodes. Nematodes, also known as roundworms, have a body structure that is symmetric along a single plane, which results in two mirror-image halves, thus exhibiting bilateral symmetry.

Furthermore, they usually have a cylindrical body shape, which means their bodies are long and narrow like a cylinder and taper at both ends. This shape helps them move through their environment easily. Additionally, nematodes have a complete digestive system with two openings: a mouth and an anus. This means that food enters through the mouth, gets digested, and waste exits through the anus.

In contrast, organisms like hydra, protozoa, and protists possess different anatomical features. Hydras, for example, typically show radial symmetry, and protozoa and protists generally do not have a well-defined body shape or bilateral symmetry as seen in nematodes. Therefore, the description fits nematodes best.