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**Question 1**
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Which of the following is not part of the electromagnetic spectrum?

**Answer Details**

The correct answer is "Alpha particle". Alpha particles are not part of the electromagnetic spectrum. Alpha particles are actually helium-4 nuclei, consisting of two protons and two neutrons, and they are emitted by some types of radioactive decay. The other options are all part of the electromagnetic spectrum. The electromagnetic spectrum includes radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. They are all forms of electromagnetic radiation characterized by different wavelengths and frequencies.

**Question 2**
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The graph above shows the relationship between sin i and sin r for a ray of light in air incident on a liquid surface. If i and r are respectively angles of incidence and refraction, deduce the refractive index of the liquid from the graph

**Question 4**
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The diagram above illustrates the velocity-time graph of the motion of a body. Calculate the total distance covered by the body

**Question 5**
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The electric potential at point P in the diagram above can be expressed as

**Question 7**
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A string of length 1.0 m vibrates in 10 loops. If the total mass of the string is 1.0 x 10^{-3} kg and the tension in it is 10N, calculate the frequency of the vibration.

**Question 8**
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A ray of light is incident on a glass block as shown in the diagram above. If the reflected and the retracted rays are perpendicular to each other, what is the refractive index of the glass relative to air.?

**Question 9**
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A platinum-resistance thermometer has a resistance of 5Ω at 0°C and 9Ω at l00°C. Assuming that resistance changes uniformly with temperature, calculate the resistance of the thermometer when the temperature is 45°C.

**Answer Details**

A platinum-resistance thermometer has a resistance of 5 Ω at 0°C and 9 Ω at 100°C, and it is assumed that resistance changes uniformly with temperature. We need to calculate the resistance of the thermometer when the temperature is 45°C. We can start by finding the change in resistance as the temperature changes from 0°C to 100°C: ΔR = 9 Ω - 5 Ω = 4 Ω This change occurs over a temperature range of 100°C - 0°C = 100°C, so the resistance changes by 4 Ω per 100°C. To find the resistance at 45°C, we can use the following proportion: (ΔR / ΔT) = (R₂ - R₁) / (T₂ - T₁) Where: ΔR = change in resistance ΔT = change in temperature R₁ = initial resistance (at 0°C) R₂ = final resistance (at 45°C) T₁ = initial temperature (0°C) T₂ = final temperature (45°C) Substituting the known values, we get: (4 Ω / 100°C) = (R₂ - 5 Ω) / (45°C - 0°C) Simplifying the equation: R₂ - 5 Ω = (4 Ω / 100°C) x 45°C R₂ - 5 Ω = 1.8 Ω R₂ = 6.8 Ω Therefore, the resistance of the platinum-resistance thermometer at 45°C is 6.8 Ω. Answer: 6.8 Ω.

**Question 10**
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A body of mass 4.2kg moving with velocity 10ms^{-1} due east, hits a stationary body of mass 2.8kg. If they stick together after collision and move with velocity V due east, calculate the value of V

**Answer Details**

In this problem, we can use the principle of conservation of momentum, which states that the total momentum of a system remains constant if no external forces act on it. The initial momentum of the system before the collision is given by: p1 = m1 * v1 where m1 is the mass of the first body (4.2 kg) and v1 is its velocity (10 m/s). p1 = 4.2 kg * 10 m/s p1 = 42 kg m/s The second body is stationary, so its initial momentum is zero: p2 = 0 kg m/s The total initial momentum of the system is therefore: p_initial = p1 + p2 p_initial = 42 kg m/s After the collision, the two bodies stick together and move with a common velocity V. The total mass of the system is the sum of the masses of the two bodies: m_total = m1 + m2 m_total = 4.2 kg + 2.8 kg m_total = 7 kg The final momentum of the system is: p_final = m_total * V According to the principle of conservation of momentum, the total initial momentum of the system is equal to the total final momentum of the system: p_initial = p_final Substituting the values we have found, we get: 42 kg m/s = 7 kg * V Solving for V, we get: V = 42 kg m/s / 7 kg V = 6 m/s Therefore, the value of V after the collision is 6 m/s due east. Thus, the correct answer is "6ms^-1".

**Question 11**
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Which of the following substances is most viscous at room temperature?

**Answer Details**

Out of the given options, palm oil is the most viscous at room temperature. Viscosity is a measure of a fluid's resistance to flow, and is affected by factors such as temperature and molecular structure of the fluid. Palm oil has a higher molecular weight and longer hydrocarbon chains compared to the other options, which leads to stronger intermolecular forces and greater resistance to flow. This makes it more viscous than water, alcohol, petrol, and kerosene at room temperature.

**Question 12**
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The diagram above illustrates a variation of the displacement y of a wave particle with time t. lf the velocity of wave is 250ms^{-1}, calculate the distance between two successive particles which are in phase

**Question 13**
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The pressure of a fixed mass of gas is 2.0 x 10^{5}Nm^{-2} at a known temperature. Assuming that the temperature remains constant, what will be the pressure of the gas if its volume is halved?

**Answer Details**

According to Boyle's law, at a constant temperature, the pressure and volume of a fixed mass of gas are inversely proportional. This means that as the volume of the gas is halved, its pressure will double. In this case, the initial pressure of the gas is 2.0 x 10^{5}Nm^{-2}. When the volume is halved, the pressure will double to 4.0 x 10^{5}Nm^{-2}. Therefore, the answer is 4.0 x 10^{5}Nm^{-2}.

**Question 14**
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A boy walks away from a plane mirror at a speed of 3 ms-1 in a direction normal to the surface of the mirror. At what speed is his image approaching him?

**Question 15**
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The diagram above represents a stationary wave set up in a string which is fixed at both ends. lf the frequency of the wave is 256Hz and the distance N1 N2 equals 1.5m, calculate the speed of the wave.

**Answer Details**

The speed of a wave can be calculated using the formula: speed = frequency x wavelength In a stationary wave, the distance between two consecutive nodes (or antinodes) represents half of the wavelength. Therefore, the wavelength of the wave in the given diagram can be calculated as: wavelength = 2 x distance(N1N2) = 2 x 1.5m = 3m Given that the frequency of the wave is 256Hz, we can now calculate its speed: speed = frequency x wavelength = 256Hz x 3m = 768ms^-1 Therefore, the speed of the wave is 768ms^{-1}.

**Question 16**
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Two spanners X and Y of lengths 15cm and 20cm respectively are used in turn to give a screw of pitch 2mm one complete rotation. If Rx and Ry are the respective velocity ratios of the spanners then the ratio Rx : Ry is

**Question 17**
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Which of the following is used in a nuclear reactor to slow down fast-moving neutrons?

**Answer Details**

In a nuclear reactor, a chain reaction is sustained by the collision of neutrons with atomic nuclei, which leads to the release of more neutrons and a large amount of energy. However, not all neutrons are capable of causing this chain reaction, as only neutrons with sufficient energy (known as fast neutrons) can interact with the nuclei to cause the chain reaction. To increase the efficiency of the chain reaction, it is desirable to slow down these fast-moving neutrons so that they are more likely to interact with atomic nuclei and cause the chain reaction to continue. This is achieved by using a material known as a moderator, which is placed in the reactor core to slow down the fast neutrons. Of the options given, the material commonly used as a moderator in nuclear reactors is graphite rods. Graphite is made of carbon atoms and has a layered structure that allows it to efficiently slow down fast neutrons. Other materials such as heavy water and beryllium can also be used as moderators, but graphite is the most commonly used. Therefore, the correct answer to the question is "Graphite rods".

**Question 18**
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The diagram above illustrates the conversion of a galvanometer of resistance 29 to an ammeter. The galvanometer gives a full-scale deflection for a current of 10mA. Calculate the value of R.

**Answer Details**

The circuit shown is a shunt or parallel circuit. We know that the full-scale deflection current of the galvanometer, I_{G} = 10mA = 10 x 10^{-3}A. Let R be the resistance of the shunt resistor. Since the galvanometer and shunt resistor are in parallel, the total current passing through the circuit is I_{T} = I_{G} + I. Here, I is the current passing through the shunt resistor. We also know that the current I should be such that the ammeter should read a full-scale deflection when the current I_{T} = 1A. According to the question, the resistance of the galvanometer is 29Ω. We can calculate the value of the current I_{T} when a potential difference of 29V is applied across the galvanometer: I_{T} = V / (R_{G} + R) where V is the applied potential difference, R_{G} is the resistance of the galvanometer, and R is the resistance of the shunt resistor. Since we know that I_{T} should be 1A when the ammeter reads full-scale deflection, we can set up the following equation: 1 = 29 / (29 + R) Solving for R gives: R = 29Ω x (1 - 1/1) = 0Ω This is not a practical value for a shunt resistor. It means that the ammeter will read zero current regardless of the actual current passing through the circuit. Therefore, we need to select an option which states that the value of R is very small. The correct option is therefore: 2.0 x 10^{-3} Ω.

**Question 19**
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The diagram above represents a portion of a micrometer screw gauge in which the horizontal scale is in millimetres. What is the reading on the instrument?

**Question 20**
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A converging lens of focal length 5cm forms a virtual image which is 10cm from the lens. How far from the lens is the object?

**Question 21**
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What is the decay constant of a radioactive element whose half-life is 3 seconds

**Answer Details**

The decay constant (λ) is a measure of the probability that a radioactive nucleus will decay per unit time. It is related to the half-life (t_{1/2}) of the radioactive element by the equation: λ = ln(2) / t_{1/2} where ln(2) is the natural logarithm of 2, which is approximately 0.693. Substituting the given half-life of 3 seconds into the equation, we have: λ = ln(2) / 3 s λ ≈ 0.231s^{-1} Therefore, the decay constant of the radioactive element is approximately 0.231s^{-1}. The option closest to this value is 0.23s^{-1}.

**Question 22**
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What is the difference in the amount of heat given out by 4kg of steam and 4kg of water when both are cooled from 100oC to 80oC? (Specific latent heat of steam = 2.260,000J kg-1) (Specific heat capacity of water =4,200 J kg-1)

**Question 23**
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The linear expansivity of a metal P is twice that of another metal Q. When these materials are heated through the same temperature change, their increase in length is the same. Calculate the ratio of the original length of P to that of Q.

**Answer Details**

Let the original length of metal P be x and the original length of metal Q be y. We know that the increase in length is given by: ΔL = L₀αΔθ where ΔL is the increase in length, L₀ is the original length, α is the coefficient of linear expansion, and Δθ is the change in temperature. Since the increase in length is the same for both metals, we can write: ΔL_{P} = ΔL_{Q} L_{P}α_{P}Δθ = L_{Q}α_{Q}Δθ L_{P}/L_{Q} = α_{Q}/α_{P} Since we are told that the linear expansivity of P is twice that of Q, we can write: α_{P} = 2α_{Q} Substituting into the equation above, we get: L_{P}/L_{Q} = α_{Q}/2α_{Q} = 1/2 Therefore, the ratio of the original length of P to that of Q is 1:2. Answer: 1:2

**Question 24**
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Calculate the amount of heat generated in an external load of resistance 89 if an alternating current of peak value 5A is passed through for 100s.

**Question 25**
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CalcuIate the power delivered by a 3-phase line if its voltage and current at 132KV and 60A respectively.

**Question 26**
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A rocket is launched from the surface of the earth. If the radius of the earth is 6.4 x 10^{6}m and the acceleration of free fall due to gravity is 1Oms^{-1} calculate the escape velocity of the rocket.

**Question 27**
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Which of the following is not a component of a d.c. electric motor?

**Answer Details**

The components of a DC electric motor include an armature, a commutator, field magnets, carbon brushes, and sometimes, brushes or slip rings. The armature is the rotating part of the motor that converts electrical energy into mechanical energy. The commutator is a device that changes the direction of the current flowing through the armature, ensuring that it continues to rotate in the same direction. The field magnets produce a magnetic field that interacts with the current flowing through the armature, causing it to rotate. Carbon brushes are used to transfer electrical current between stationary wires and moving parts of the motor, such as the commutator or slip rings. Slip rings are used in some types of motors as an alternative to the commutator to transfer electrical current between the stationary wires and the rotating parts of the motor. Therefore, the component that is not a component of a DC electric motor is slip rings. Although slip rings can be used in some types of electric motors, they are not commonly used in DC electric motors. Instead, DC motors typically use a commutator to transfer electrical current between the stationary wires and the rotating armature. So the correct answer to the question is "Slip rings".

**Question 28**
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The resistance in a series R-C circuit is 5 Ω. If the impedance of the circuit is 13 Ω, calculate the reactance of the capacitor

**Answer Details**

In a series R-C circuit, the total impedance is given by: Z = √(R^2 + Xc^2) where R is the resistance and Xc is the reactance of the capacitor. Since the impedance of the circuit is 13 Ω and the resistance is 5 Ω, we have: 13 = √(5^2 + Xc^2) Squaring both sides, we get: 169 = 25 + Xc^2 Simplifying, we get: Xc^2 = 144 Taking the square root of both sides, we get: Xc = ±12 Since we are looking for the magnitude of the reactance, we take the positive value: Xc = 12 Ω Therefore, the reactance of the capacitor is 12 Ω.

**Question 29**
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When a ray of light is incident normally on an air- glass interface, its angle of refraction is

**Answer Details**

When a ray of light is incident normally on an air-glass interface, its angle of refraction is 0 degrees. This is because when light travels from one medium to another, it changes direction, a phenomenon known as refraction. The amount of refraction depends on the angle at which the light enters the second medium, as well as the properties of the two media, such as their refractive indices. In the case of an air-glass interface, since the angle of incidence is normal, that is, the ray of light is perpendicular to the surface, the angle of refraction is also zero. This means that the light continues to travel in a straight line without changing its direction. So the correct answer to the question is 0 degrees.

**Question 30**
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Soft iron is used in making the armature of an electric bell because it

**Answer Details**

Soft iron is used in making the armature of an electric bell because it loses its magnetism readily. This is due to its low coercivity, which means that it is easily magnetized and demagnetized. In an electric bell, the armature needs to be magnetized and demagnetized rapidly in order to vibrate back and forth, striking the bell and producing the sound. If the armature were made of a material that retained its magnetism for a long time, it would not vibrate back and forth as required, and the bell would not ring properly. Therefore, soft iron is an ideal material for the armature of an electric bell because it can be easily magnetized and demagnetized, allowing the bell to ring properly.

**Question 31**
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The walls and ceilings of many standard auditoria are covered with perforated pads to

**Answer Details**

The perforated pads on the walls and ceilings of standard auditoria are there to reduce the effect of reverberations of sound waves. When sound waves are produced in a room, they bounce off the walls, floor, and ceiling, creating an echo-like effect that can make it difficult to hear and understand speech or music clearly. The perforations in the pads allow sound waves to pass through them and get absorbed by a layer of sound-absorbing material behind them. This reduces the amount of sound waves bouncing around the room, leading to clearer and more intelligible sound. The pads do not increase the intensity or loudness of sound waves, nor do they increase the interference effect or decrease the frequency of sound waves.

**Question 32**
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A ball of mass 5.0kg hits a smooth vertical wall normally with a speed of 2ms^{-1} and rebounds with the same speed. Determine the impulse experienced by the ball

**Answer Details**

The impulse experienced by the ball can be calculated using the impulse-momentum theorem, which states that the impulse on an object is equal to the change in momentum of the object. In this case, the ball has an initial momentum of p = mv, where m is its mass and v is its velocity, and it rebounds with the same speed, but in the opposite direction. This means that the final momentum of the ball is -mv. The change in momentum, therefore, is: Δp = -mv - mv = -2mv The impulse experienced by the ball is equal to the change in momentum, so: impulse = Δp = -2mv Substituting the given values, we get: impulse = -2(5.0 kg)(2 m/s) = -20.0 kg m/s Since impulse is a vector quantity, its magnitude is always positive. Therefore, we take the absolute value of the calculated impulse to get: impulse = 20.0 kg m/s So the correct answer to the question is 20.0 kg m/s.

**Question 33**
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The main reason why rice cooks faster in a pressure cooker than in cooking pot is that

**Answer Details**

The main reason why rice cooks faster in a pressure cooker than in a cooking pot is that the boiling point of water in the cooker is raised. In a pressure cooker, water boils at a higher temperature due to the increased pressure inside the cooker. This increase in temperature means that the rice cooks faster as it is exposed to higher temperatures than it would be in a cooking pot. Additionally, less heat escapes from the cooker, and the vapour pressure in the cooker is constant, contributing to the rice cooking faster.

**Question 34**
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A body of mass 2kg is suspended from the ceiling of a lift with a light inextensible string. lf the lift moves upwards with acceleration of 2ms^{-2}, calculate the magnitude of the tension in the string (g = 1Oms^{-2})

**Answer Details**

When a body of mass is suspended by a string, the tension in the string is equal to the weight of the body. The weight of the body is given by the formula: Weight = mass x gravity where "mass" is the mass of the body and "gravity" is the acceleration due to gravity. In this case, the mass of the body is 2 kg and the acceleration due to gravity is 10 m/s^2. However, the lift is accelerating upwards with an acceleration of 2 m/s^2. This means that the net acceleration of the body (relative to the lift) is the difference between the acceleration due to gravity and the acceleration of the lift: Net acceleration = acceleration due to gravity - acceleration of the lift Net acceleration = 10 m/s^2 - 2 m/s^2 Net acceleration = 8 m/s^2 Therefore, the net force acting on the body (relative to the lift) is given by the formula: Net force = mass x net acceleration Substituting the given values, we have: Net force = 2 kg x 8 m/s^2 Net force = 16 N Since the tension in the string is equal to the net force acting on the body, the tension in the string is 16 N. Therefore, the correct answer to the question is "16N".

**Question 35**
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The distance between two successive crests of a water is 1m. lf a particle on the surface of the water makes two complete vertical oscillations in 1 second, calculate the speed of the wave

**Answer Details**

The distance between two successive crests of a wave is called its wavelength, denoted by λ. In this question, the wavelength is given as 1m. The number of complete oscillations (or cycles) of a particle on the surface of the water in 1 second is called the frequency, denoted by f. In this question, the frequency is given as 2 cycles per second (or 2 Hz). The speed of a wave is given by the formula: v = f × λ Substituting the given values, we get: v = 2 Hz × 1m v = 2 m/s Therefore, the speed of the wave is 2 m/s. The correct answer is option (C) 2.0 ms^-1.

**Question 36**
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Lenz's law of electromagnetic induction states that

**Answer Details**

Lenz's law of electromagnetic induction is a fundamental law in physics that describes the relationship between the change in magnetic flux and the induced electromotive force (EMF) and current. The law states that when there is a change in the magnetic flux through a closed loop, an EMF is induced in the loop that is proportional to the rate of change of the flux. Furthermore, the direction of the induced EMF is such that it opposes the change that produced it. In other words, the induced current flows in a direction that creates a magnetic field that opposes the change in the original magnetic field. This means that if the magnetic flux through a circuit increases, the induced current will create a magnetic field that opposes the increase in flux. Similarly, if the flux through the circuit decreases, the induced current will create a magnetic field that opposes the decrease in flux. Therefore, among the given options, the correct answer is (B) the induced current in a conductor is in such a direction as to oppose the change producing it.

**Question 37**
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Two simple pendula x and y make 400 and 500 oscillations respectively in equal time. If the period of oscillation of x is 1.5 seconds, what is the period of oscillation of y?

**Answer Details**

The number of oscillations of a pendulum in a given time depends on its period of oscillation. The period is the time taken for one complete oscillation. The relationship between the period and the number of oscillations is direct; that is, as the period of a pendulum decreases, the number of oscillations it makes in a given time increases. In this question, we are given that the period of oscillation of pendulum x is 1.5 seconds, and it makes 400 oscillations in equal time. We are also given that pendulum y makes 500 oscillations in equal time. Since both pendula are making oscillations in equal time, we can assume that the time taken for each pendulum to make one oscillation is the same. To find the period of oscillation of pendulum y, we can use the relationship between the period and the number of oscillations. If pendulum x with a period of 1.5 seconds makes 400 oscillations in equal time, then the total time taken for 400 oscillations is: Time taken by pendulum x = 400 x 1.5 seconds = 600 seconds Since pendulum y makes 500 oscillations in the same time, the period of oscillation of y can be calculated as follows: Time taken by pendulum y for 500 oscillations = 600 seconds Period of pendulum y = Total time taken / Number of oscillations Period of pendulum y = 600 seconds / 500 oscillations Period of pendulum y = 1.2 seconds Therefore, the period of oscillation of pendulum y is 1.2 seconds.

**Question 38**
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The speed of sound in air is 330ms^{-1}. How far from the centre of a storm is an observer who hears a thunder clap 2s after the lightning flash? (Neglect the time taken by light to travel to the observer)

**Question 39**
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The heating element in an electric kettle is usually located near the bottom of the kettle because

**Answer Details**

The heating element in an electric kettle is usually located near the bottom of the kettle because of convection currents. When the heating element is turned on, it heats up the water in contact with it. Hot water is less dense than cold water, so it rises to the top of the kettle while the colder water sinks to the bottom. This creates a convection current, where the hot water at the top of the kettle is replaced by the colder water at the bottom, which in turn is heated by the heating element. This process continues until all the water in the kettle is heated to the desired temperature. If the heating element were located near the top of the kettle, the convection current would be less efficient because the hot water at the top would not mix as easily with the colder water at the bottom. By placing the heating element near the bottom of the kettle, the convection currents are more effective at carrying the heat to all parts of the water, resulting in faster heating and more efficient energy use. Therefore, the correct answer is option (D) - the convectional currents which are set up can carry heat to all parts of the water.

**Question 40**
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The diagram above illustrates an isolated metal sphere carrying charge W in a medium whose permittivity is so. The magnitude of the electric field intensity at P can be expressed as

**Answer Details**

The electric field intensity at point P due to the isolated charged sphere is given by Coulomb's law, which states that the magnitude of the electric field intensity is directly proportional to the charge on the sphere and inversely proportional to the square of the distance between the sphere and point P. Mathematically, it is expressed as: E = Q/(4πε_{o}r^{2}) where E is the electric field intensity, Q is the charge on the sphere, ε_{o} is the permittivity of the medium, and r is the distance between the sphere and point P. Therefore, the correct option is (b) Q/(4πε_{o}r^{2}).

**Question 41**
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A ray of light strikes a plane mirror at a glancing angle of 50^{o}. Calculate the angle between the incident and reflected rays

**Question 42**
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ln the diagram above, the resistor has a resistance 8 ? while the reactances of the inductor and the capacitor are 10 ? and 16 ? respectively Calculate the current in the circuit

**Question 43**
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A sound wave of velocity 350 ms^{-1} is directed towards the surface of water. lf the ratio of the wavelength of sound in water to that in air is 425:100, calculate the velocity on the wave in water

**Answer Details**

The velocity of a sound wave depends on the properties of the medium through which it is traveling. The formula for the velocity of a sound wave is: v = λf where v is the velocity, λ is the wavelength, and f is the frequency of the wave. In this question, we are given that the velocity of sound in air is 350 ms^-1 and the ratio of the wavelength of sound in water to that in air is 425:100. Let's assume that the frequency of the wave remains constant as it passes from air into water. If the wavelength of the sound wave in air is λ_{air}, then the wavelength of the same wave in water is: λ_{water} = (425/100)λ_{air} = 4.25λ_{air} Now we can use the formula for the velocity of a sound wave to find the velocity of the wave in water: v_{water} = λ_{water}f Since the frequency of the wave remains constant, we can write: v_{water} = (4.25λ_{air})f We know that the velocity of the wave in air is 350 ms^-1, and we can write: v_{air} = λ_{air}f Solving for f, we get: f = v_{air}/λ_{air} Substituting this expression for f into the previous equation, we get: v_{water} = (4.25λ_{air})v_{air}/λ_{air} Simplifying, we get: v_{water} = 4.25v_{air} Substituting the given value for the velocity of sound in air, we get: v_{water} = 4.25 x 350 ms^-1 Simplifying, we get: v_{water} = 1487.5 ms^-1 Therefore, the velocity of the wave in water is 1487.5 ms^-1. Option (D) is the correct answer.

**Question 44**
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A wire of length 100cm and cross-sectional area of 2.0 x 10^{-3}cm^{2} has a resistance of 0.10 Ω. Calculate its electrical conductivity.

**Answer Details**

Electrical conductivity is a measure of how easily a material can conduct electricity. It is the reciprocal of electrical resistivity. The formula for electrical conductivity is given by: σ = 1/ρ Where σ is electrical conductivity and ρ is electrical resistivity. We are given the length (L) of the wire as 100 cm, the cross-sectional area (A) as 2.0 x 10^-3 cm^2, and the resistance (R) as 0.10 Ω. We can use Ohm's law to calculate the resistivity (ρ): R = ρ*L/A ρ = RA/L Substituting the given values, we get: ρ = (0.10 Ω)*(2.0 x 10^-3 cm^2)/100 cm ρ = 2.0 x 10^-6 Ω cm Now, we can calculate the electrical conductivity using the formula: σ = 1/ρ σ = 1/(2.0 x 10^-6 Ω cm) σ = 5.0 x 10^5 Ω^-1 cm^-1 Therefore, the electrical conductivity of the wire is 5.0 x 10^5 Ω^-1 cm^-1. Answer: 5.0 x 10^5 Ω^-1 cm^-1

**Question 45**
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Which of the following is used in a nuclear reactor to slow down fast-moving neutrons?

**Question 46**
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The saturated vapour pressure of a liquid increases as the

**Answer Details**

The saturated vapor pressure of a liquid increases as the temperature of the liquid increases. When a liquid is heated, its molecules gain kinetic energy and move faster, causing more molecules to escape into the gas phase. This increases the concentration of vapor molecules in the air above the liquid, leading to an increase in the vapor pressure. Conversely, if the temperature of the liquid decreases, the vapor pressure will decrease as fewer molecules have enough energy to escape into the gas phase. The volume and mass of the liquid do not directly affect the saturated vapor pressure.

**Question 47**
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The magnitude of the force required to make an object of mass M move with speed V in a circular path of radius R is given by the expression.

**Answer Details**

The magnitude of the force required to make an object of mass M move with speed V in a circular path of radius R is given by the expression mv²/r. This is known as the centripetal force. When an object moves in a circle, it experiences a change in direction which means it is accelerating. Since there is acceleration, there must be a force acting on the object. The centripetal force is the force that acts on an object moving in a circular path, directed towards the center of the circle, and is necessary to keep the object moving in a circular path. The magnitude of this force is directly proportional to the mass of the object, the square of its velocity and inversely proportional to the radius of the circular path. Thus, the correct option is (C) mv²/r.

**Question 48**
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Which of the following instruments produces sound by the vibration of air column?

**Answer Details**

The instrument that produces sound by the vibration of an air column is a flute. The flute is a wind instrument that produces sound by blowing air across the mouthpiece. The air column inside the flute vibrates and produces sound waves, which then travel through the instrument and out of the end, producing the sound that we hear. In contrast, a piano produces sound through the vibration of strings, a guitar produces sound through the vibration of strings, a handbell produces sound through the vibration of metal, and a talking drum produces sound through the vibration of a stretched membrane.

**Question 49**
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A cell of e.m.f. 1.5V is connected in series with a resistor of resistance 39. A high-resistance voltmeter connected across the cell registers only 0.9V. Calculate the internal resistance of the cell

**Question 50**
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Which of the following particles/rays do not originate from the nucleus of an atom?

**Question 51**
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The count rate of an alpha-particle source is 400 per minute. If the half-life of the source is 5 days, what would be the count rate per minute after 15 days?

**Answer Details**

The count rate of an alpha-particle source refers to the number of alpha particles emitted by the source in one minute. The half-life of a radioactive source is the time it takes for half of the radioactive atoms to decay. If the count rate of the alpha-particle source is 400 per minute and the half-life of the source is 5 days, this means that after 5 days, the count rate will decrease to 200 per minute (half of 400). After another 5 days (a total of 10 days), the count rate will decrease to 100 per minute (half of 200). After another 5 days (a total of 15 days), the count rate will decrease to 50 per minute (half of 100). Therefore, the count rate per minute after 15 days will be 50, and the correct answer is option (C) 50.

**Question 52**
**Report**

When a ray of light is incident normally on an air- glass interface, its angle of refraction is

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