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Tamil Nadu SSLC Science study materials
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Tamil Nadu SSLC Science practice questions

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Question 1Physics – Laws of Motion, Optics, Electricity and Magnetism

A body of mass 5 kg is pushed with a constant force of 20 N on a frictionless horizontal surface. What is the acceleration of the body?

  1. 100 m s⁻²
  2. 25 m s⁻²
  3. 4 m s⁻² Correct answer.
  4. 0.25 m s⁻²

Explanation

Newton's second law gives F = ma, so acceleration equals force divided by mass. Dividing 20 N by 5 kg yields 4 m s⁻², and because the surface is frictionless no opposing force reduces this value.

Question 2Physics – Laws of Motion, Optics, Electricity and Magnetism

Which quantity is a measure of the inertia of a body?

  1. Its momentum
  2. Its velocity
  3. Its mass Correct answer.
  4. Its weight

Explanation

Inertia is the tendency of a body to resist a change in its state of rest or uniform motion, and mass is the direct measure of this property. Weight depends on gravity, while velocity and momentum describe motion rather than resistance to change.

Question 3Physics – Laws of Motion, Optics, Electricity and Magnetism

A cricketer catches a fast-moving ball by drawing his hands backwards along the direction of the ball. Which law of motion best explains why this reduces the sting of the catch?

  1. The law of conservation of momentum, because total momentum becomes zero
  2. Newton's first law, because the ball continues in uniform motion
  3. Newton's second law, because the stopping force is reduced when the stopping time increases Correct answer.
  4. Newton's third law, because the hand exerts an equal and opposite force

Explanation

For a given change in momentum, the force is inversely proportional to the time over which the change occurs, as expressed by F = Δp/Δt. Drawing the hands back lengthens the stopping time, so the average force on the hands is smaller and the sting is reduced.

Question 4Physics – Laws of Motion, Optics, Electricity and Magnetism

A force of 10 N acts on a body for 3 s. What is the impulse imparted to the body?

  1. 3.3 N s
  2. 13 N s
  3. 0.3 N s
  4. 30 N s Correct answer.

Explanation

Impulse is the product of force and the time for which it acts, so J = F × t. Multiplying 10 N by 3 s gives 30 N s, which also equals the change in momentum of the body.

Question 5Physics – Laws of Motion, Optics, Electricity and Magnetism

Two bodies of masses 2 kg and 6 kg are pushed with the same force. How do their accelerations compare?

  1. The 2 kg body has three times the acceleration of the 6 kg body Correct answer.
  2. The 2 kg body has one-third the acceleration of the 6 kg body
  3. The 6 kg body has three times the acceleration of the 2 kg body
  4. Both bodies have equal acceleration

Explanation

From F = ma, acceleration is inversely proportional to mass when the force is the same. The lighter body of 2 kg therefore has 6/2 = 3 times the acceleration of the 6 kg body.

Question 6Physics – Laws of Motion, Optics, Electricity and Magnetism

A book rests on a table without moving. Which statement about the forces on the book is correct?

  1. The normal force is greater than the weight because the table is rigid
  2. The normal force and the weight form an action-reaction pair acting on different bodies
  3. The normal force and the weight are equal in magnitude and opposite in direction, so they balance Correct answer.
  4. The book experiences no forces because it is at rest

Explanation

Because the book is in equilibrium, the net force on it is zero. The upward normal force from the table and the downward weight both act on the book and are equal in magnitude, so they balance each other.

Question 7Physics – Laws of Motion, Optics, Electricity and Magnetism

Why does a rocket move forward when its exhaust gases are ejected backward?

  1. The gases push against the surrounding air, which pushes the rocket forward
  2. The backward momentum of the gases is balanced by the forward momentum of the rocket Correct answer.
  3. The rocket's weight decreases as fuel burns, so it rises
  4. The hot gases create a vacuum that pulls the rocket forward

Explanation

The total momentum of the rocket and its exhaust is conserved. Ejecting gases backward gives them backward momentum, so the rocket acquires an equal forward momentum and moves forward even in space.

Question 8Physics – Laws of Motion, Optics, Electricity and Magnetism

Which of the following is a scalar quantity?

  1. Speed Correct answer.
  2. Velocity
  3. Force
  4. Acceleration

Explanation

Scalars have magnitude only, while vectors have both magnitude and direction. Speed is a scalar, whereas velocity, acceleration and force all require a direction to be fully specified.

Question 9Physics – Laws of Motion, Optics, Electricity and Magnetism

A concave mirror has a focal length of 10 cm. An object is placed 30 cm in front of it. Where is the image formed?

  1. 15 cm in front of the mirror Correct answer.
  2. 30 cm behind the mirror
  3. 7.5 cm in front of the mirror
  4. 10 cm in front of the mirror

Explanation

Using the mirror formula 1/f = 1/v + 1/u with f = −10 cm and u = −30 cm, we get 1/v = −1/10 + 1/30 = −2/30, so v = −15 cm. The negative sign shows a real image 15 cm in front of the mirror.

Question 10Physics – Laws of Motion, Optics, Electricity and Magnetism

An object is placed between the pole and the principal focus of a concave mirror. What is the nature of the image formed?

  1. Real, inverted and same size
  2. Real, inverted and diminished
  3. Virtual, erect and diminished
  4. Virtual, erect and magnified Correct answer.

Explanation

When the object lies between the pole and the focus of a concave mirror, the reflected rays diverge. They appear to meet behind the mirror, giving a virtual, erect and magnified image, as in a shaving mirror.

Question 11Physics – Laws of Motion, Optics, Electricity and Magnetism

A ray of light passes from air into glass. Which statement describes the change correctly?

  1. The ray bends away from the normal because glass is optically denser than air
  2. The ray bends towards the normal because its speed increases in glass
  3. The ray bends towards the normal because glass is optically denser than air Correct answer.
  4. The ray continues undeviated because the frequency does not change

Explanation

When light enters a denser medium, its speed decreases and it bends towards the normal, in accordance with Snell's law. Glass has a higher refractive index than air, so the refracted ray lies closer to the normal.

Question 12Physics – Laws of Motion, Optics, Electricity and Magnetism

The refractive index of a medium is 1.5. What is the speed of light in that medium? (Speed of light in vacuum = 3 × 10⁸ m s⁻¹)

  1. 3 × 10⁸ m s⁻¹
  2. 1.5 × 10⁸ m s⁻¹
  3. 4.5 × 10⁸ m s⁻¹
  4. 2 × 10⁸ m s⁻¹ Correct answer.

Explanation

Refractive index n equals the speed of light in vacuum divided by the speed in the medium, so v = c/n. Dividing 3 × 10⁸ m s⁻¹ by 1.5 gives 2 × 10⁸ m s⁻¹, which is less than the vacuum speed as expected.

Question 13Physics – Laws of Motion, Optics, Electricity and Magnetism

A convex lens of focal length 20 cm forms a real image at 60 cm from the lens. What is the object distance?

  1. 30 cm Correct answer.
  2. 40 cm
  3. 15 cm
  4. 60 cm

Explanation

Using the lens formula 1/f = 1/v − 1/u with f = 20 cm and v = 60 cm, we get 1/u = 1/60 − 1/20 = −2/60, so u = −30 cm. The object therefore lies 30 cm in front of the lens.

Question 14Physics – Laws of Motion, Optics, Electricity and Magnetism

Which defect of vision is corrected by using a convex lens of suitable power?

  1. Hypermetropia Correct answer.
  2. Astigmatism
  3. Myopia
  4. Presbyopia

Explanation

In hypermetropia, or long-sightedness, the eye focuses images behind the retina because the lens is too weak or the eyeball is too short. A convex converging lens adds the needed power so the image falls on the retina.

Question 15Physics – Laws of Motion, Optics, Electricity and Magnetism

White light passes through a glass prism and splits into its constituent colours. Which colour is deviated the most?

  1. Yellow
  2. Red
  3. Violet Correct answer.
  4. Green

Explanation

Dispersion occurs because the refractive index of glass varies with wavelength. Violet light has the shortest wavelength and the highest refractive index in glass, so it is deviated the most, while red is deviated the least.

Question 16Physics – Laws of Motion, Optics, Electricity and Magnetism

An electric heater of resistance 22 Ω is connected to a 220 V supply. What current flows through it?

  1. 10 A Correct answer.
  2. 4840 A
  3. 2.2 A
  4. 0.1 A

Explanation

Ohm's law states that current equals voltage divided by resistance, I = V/R. Dividing 220 V by 22 Ω gives 10 A, which is a typical current for a domestic heater.

Question 17Physics – Laws of Motion, Optics, Electricity and Magnetism

Three resistors of 2 Ω, 3 Ω and 5 Ω are connected in series. What is the effective resistance of the combination?

  1. 30 Ω
  2. 0.97 Ω
  3. 3.3 Ω
  4. 10 Ω Correct answer.

Explanation

In a series combination, the effective resistance is the sum of the individual resistances. Adding 2 Ω, 3 Ω and 5 Ω gives 10 Ω, and the same current flows through each resistor.

Question 18Physics – Laws of Motion, Optics, Electricity and Magnetism

Two resistors of 6 Ω and 3 Ω are connected in parallel. What is the effective resistance?

  1. 9 Ω
  2. 0.5 Ω
  3. 2 Ω Correct answer.
  4. 4.5 Ω

Explanation

For two resistors in parallel, the reciprocal of the effective resistance is the sum of the reciprocals: 1/R = 1/6 + 1/3 = 1/2. Hence R = 2 Ω, which is smaller than either individual resistance.

Question 19Physics – Laws of Motion, Optics, Electricity and Magnetism

An electric bulb marked 100 W, 250 V is operated at its rated voltage. What is its resistance?

  1. 25000 Ω
  2. 0.4 Ω
  3. 2.5 Ω
  4. 625 Ω Correct answer.

Explanation

Power is given by P = V²/R, so R = V²/P. Substituting 250 V and 100 W, we get R = 62500/100 = 625 Ω, the resistance of the filament at its working temperature.

Question 20Physics – Laws of Motion, Optics, Electricity and Magnetism

Which effect of electric current is used in an electric iron?

  1. Chemical effect
  2. Magnetic effect
  3. Heating effect Correct answer.
  4. Photoelectric effect

Explanation

When current flows through the high-resistance heating element of an iron, electrical energy is converted into heat, as described by Joule's law. The magnetic effect is used in motors and bells, and the chemical effect in electrolysis.

Question 21Physics – Laws of Motion, Optics, Electricity and Magnetism

A current-carrying straight conductor is placed perpendicular to a uniform magnetic field. Which change will double the magnetic force on it?

  1. Doubling the current while keeping the length and field unchanged Correct answer.
  2. Halving the magnetic field strength
  3. Reversing the direction of the current
  4. Aligning the conductor parallel to the magnetic field

Explanation

The force on a straight conductor is F = B I L sin θ, so it is directly proportional to the current. Doubling the current doubles the force, whereas reversing the current only reverses the force's direction.

Question 22Physics – Laws of Motion, Optics, Electricity and Magnetism

According to Fleming's left-hand rule, the forefinger, middle finger and thumb of the left hand indicate respectively:

  1. Magnetic field, current and force on the conductor Correct answer.
  2. Current, magnetic field and force on the conductor
  3. Force, current and magnetic field
  4. Magnetic field, force and current

Explanation

Fleming's left-hand rule gives the direction of the force on a current-carrying conductor in a magnetic field. The forefinger points along the field, the middle finger along the current, and the thumb along the force.

Question 23Physics – Laws of Motion, Optics, Electricity and Magnetism

Why is the magnetic field inside a long solenoid uniform?

  1. The solenoid is made of a magnetic material
  2. The solenoid has no resistance
  3. The current in the solenoid is constant everywhere
  4. The fields of the individual turns add up along the axis and cancel outside Correct answer.

Explanation

Inside a long solenoid, the magnetic fields due to each turn point in the same direction along the axis and reinforce each other. This superposition produces a nearly uniform field inside, while the fields largely cancel outside.

Question 24Physics – Laws of Motion, Optics, Electricity and Magnetism

A step-down transformer has 1000 turns in its primary and 100 turns in its secondary. If the primary voltage is 220 V, what is the secondary voltage?

  1. 22 V Correct answer.
  2. 110 V
  3. 2200 V
  4. 2.2 V

Explanation

For an ideal transformer, the voltage ratio equals the turns ratio: Vs/Vp = Ns/Np. Substituting 220 V and 100/1000 gives Vs = 220 × 0.1 = 22 V, consistent with a step-down transformer.

Question 25Physics – Laws of Motion, Optics, Electricity and Magnetism

An electric motor converts electrical energy into mechanical energy. Which principle explains its working?

  1. A changing magnetic flux induces an emf in a coil
  2. A current-carrying coil in a magnetic field experiences a torque Correct answer.
  3. Like magnetic poles attract each other
  4. A current-carrying conductor produces a magnetic field only

Explanation

In an electric motor, the two sides of a current-carrying coil lie in a magnetic field and experience forces in opposite directions. These forces constitute a torque that rotates the coil, converting electrical energy into mechanical work.

Question 26Physics – Laws of Motion, Optics, Electricity and Magnetism

A passenger standing in a moving bus falls backward when the bus starts suddenly. Which property of the passenger explains this?

  1. Inertia of rest Correct answer.
  2. Momentum of the bus
  3. Reaction of the floor
  4. Inertia of motion

Explanation

A body at rest tends to remain at rest unless an external force acts on it; this is the law of inertia. When the bus lurches forward, the passenger's lower body moves with the floor while the upper body stays at rest, so the passenger appears to fall backward. This is inertia of rest, not inertia of motion.

Question 27Physics – Laws of Motion, Optics, Electricity and Magnetism

The SI unit of force is expressed in terms of base units as:

  1. kg m s⁻² Correct answer.
  2. kg m⁻¹ s⁻²
  3. kg m s⁻¹
  4. kg m² s⁻²

Explanation

Force equals mass times acceleration, so its unit is the kilogram metre per second squared, called the newton. Since acceleration has units of m s⁻², multiplying by kg gives kg m s⁻². The other combinations correspond to energy, momentum and a quantity with inverse length.

Question 28Physics – Laws of Motion, Optics, Electricity and Magnetism

A force of 20 N acts on a body of mass 5 kg for 4 s, starting from rest. What is the change in velocity of the body?

  1. 80 m s⁻¹
  2. 100 m s⁻¹
  3. 4 m s⁻¹
  4. 16 m s⁻¹ Correct answer.

Explanation

By Newton's second law the acceleration is F/m = 20/5 = 4 m s⁻². Using v = u + at with u = 0 gives v = 4 × 4 = 16 m s⁻¹. The change in velocity equals the final velocity here because the body started from rest.

Question 29Physics – Laws of Motion, Optics, Electricity and Magnetism

A cricketer moves his hands backwards while catching a fast ball. This is done to:

  1. Increase the time of impact and so reduce the force on the hands Correct answer.
  2. Increase the rate of change of momentum
  3. Increase the momentum change of the ball
  4. Reduce the mass of the ball during impact

Explanation

The impulse needed to stop the ball is fixed by its momentum change. By increasing the time over which the ball is brought to rest, the average force F = Δp/Δt becomes smaller. Hence the hands experience less force.

Question 30Physics – Laws of Motion, Optics, Electricity and Magnetism

Two bodies of masses 4 kg and 2 kg move towards each other with velocities 3 m s⁻¹ and 6 m s⁻¹ respectively and stick together after collision. What is the velocity of the combined body?

  1. Zero Correct answer.
  2. 1 m s⁻¹ towards the 4 kg body
  3. 3 m s⁻¹ towards the 4 kg body
  4. 2 m s⁻¹ towards the 2 kg body

Explanation

Taking the direction of the 4 kg body as positive, total momentum = 4×3 − 2×6 = 12 − 12 = 0. Momentum is conserved in the collision, so the combined mass of 6 kg also has zero momentum. The combined body therefore remains at rest.

Question 31Physics – Laws of Motion, Optics, Electricity and Magnetism

A body of weight 50 N is pulled along a horizontal surface by a force applied at 60° to the horizontal. If the applied force is 40 N, what is the horizontal component that actually tends to move the body?

  1. 40 N
  2. 34.6 N
  3. 20 N Correct answer.
  4. 46.6 N

Explanation

The horizontal component of a force F at angle θ to the horizontal is F cos θ. Here 40 × cos 60° = 40 × 0.5 = 20 N. Only this component acts along the surface to move the body.

Question 32Physics – Laws of Motion, Optics, Electricity and Magnetism

A ray of light strikes a plane mirror at an angle of incidence of 30°. What is the angle between the incident ray and the reflected ray?

  1. 90°
  2. 120°
  3. 60° Correct answer.
  4. 30°

Explanation

By the law of reflection the angle of reflection equals the angle of incidence, so both are 30° measured from the normal. The angle between the incident and reflected rays is the sum of these two angles, 30° + 30° = 60°.

Question 33Physics – Laws of Motion, Optics, Electricity and Magnetism

An object is placed at the centre of curvature of a concave mirror. The image formed is:

  1. Real, inverted and of the same size as the object Correct answer.
  2. Virtual, erect and magnified
  3. Real, inverted and diminished
  4. Virtual, erect and of the same size

Explanation

When the object is at the centre of curvature of a concave mirror, the reflected rays converge at the centre of curvature itself. The image is therefore real, inverted and exactly the same size as the object.

Question 34Physics – Laws of Motion, Optics, Electricity and Magnetism

A convex mirror always forms an image that is:

  1. Virtual, erect and diminished Correct answer.
  2. Real, erect and magnified
  3. Virtual, inverted and magnified
  4. Real, inverted and diminished

Explanation

A convex mirror diverges the reflected rays, so the image is always formed behind the mirror. Such an image is virtual, erect and smaller than the object, whatever the object distance. This is why convex mirrors are used as rear-view mirrors.

Question 35Physics – Laws of Motion, Optics, Electricity and Magnetism

The magnification produced by a spherical mirror is −2. What does this indicate?

  1. The image is virtual, inverted and half the size of the object
  2. The image is real, erect and half the size of the object
  3. The image is real, inverted and twice the size of the object Correct answer.
  4. The image is virtual, erect and twice the size of the object

Explanation

For mirrors, magnification m = −v/u, and a negative value means the image is real and inverted. The magnitude 2 means the image is twice as tall as the object. Hence the image is real, inverted and magnified.

Question 36Physics – Laws of Motion, Optics, Electricity and Magnetism

A convex lens of focal length 10 cm forms an image at 15 cm from the lens. What is the object distance?

  1. 30 cm Correct answer.
  2. 25 cm
  3. 5 cm
  4. 6 cm

Explanation

Using the lens formula 1/f = 1/v − 1/u with f = 10 cm and v = 15 cm gives 1/u = 1/15 − 1/10 = (2 − 3)/30 = −1/30. Hence u = −30 cm, so the object is 30 cm from the lens on the opposite side.

Question 37Physics – Laws of Motion, Optics, Electricity and Magnetism

A person suffering from myopia can see clearly only up to 2 m. Which lens is required to correct this defect?

  1. A concave lens of focal length 2 m Correct answer.
  2. A convex lens of focal length 2 m
  3. A convex lens of focal length 0.5 m
  4. A concave lens of focal length 0.5 m

Explanation

Myopia is short-sightedness, in which the image of a distant object forms in front of the retina. A concave lens of focal length equal to the far point, here 2 m, diverges the rays so that the image falls on the retina. Convex lenses would worsen the defect.

Question 38Physics – Laws of Motion, Optics, Electricity and Magnetism

The power of a lens of focal length 25 cm is:

  1. +0.25 dioptre
  2. +4 dioptre Correct answer.
  3. +25 dioptre
  4. −4 dioptre

Explanation

Power P = 1/f with f in metres, so f = 0.25 m gives P = 1/0.25 = 4 dioptre. A convex lens has positive power, so the answer is +4 D.

Question 39Physics – Laws of Motion, Optics, Electricity and Magnetism

Which statement correctly describes total internal reflection?

  1. It occurs when light travels from a denser to a rarer medium at an angle less than the critical angle
  2. It occurs when light travels from a denser to a rarer medium at an angle greater than the critical angle Correct answer.
  3. It occurs when light strikes a plane mirror at normal incidence
  4. It occurs when light travels from a rarer to a denser medium at any angle

Explanation

Total internal reflection needs two conditions: the light must travel from a denser to a rarer medium, and the angle of incidence must exceed the critical angle for that pair of media. Under these conditions no refracted ray emerges and all the light is reflected back into the denser medium.

Question 40Physics – Laws of Motion, Optics, Electricity and Magnetism

A glass slab of thickness 6 cm and refractive index 1.5 is placed over a coin. At what apparent depth does the coin appear when viewed from above?

  1. 6 cm
  2. 9 cm
  3. 4 cm Correct answer.
  4. 2 cm

Explanation

The apparent depth is the real thickness divided by the refractive index: 6/1.5 = 4 cm. The coin appears raised because light bends away from the normal on leaving the glass.

Question 41Physics – Laws of Motion, Optics, Electricity and Magnetism

Which of the following is a non-ohmic conductor?

  1. A semiconductor diode Correct answer.
  2. A copper wire at constant temperature
  3. A carbon resistor at constant temperature
  4. A nichrome wire at constant temperature

Explanation

A conductor is ohmic when the current is directly proportional to the potential difference, giving a straight-line V–I graph. A semiconductor diode conducts appreciably only in one direction and its V–I graph is not a straight line, so it is non-ohmic.

Question 42Physics – Laws of Motion, Optics, Electricity and Magnetism

A wire of resistance 12 Ω is stretched uniformly to twice its original length. What is its new resistance?

  1. 48 Ω Correct answer.
  2. 24 Ω
  3. 6 Ω
  4. 12 Ω

Explanation

Stretching keeps the volume constant, so doubling the length halves the area of cross-section. Resistance R = ρl/A then becomes 2 × 2 = 4 times the original, that is 12 × 4 = 48 Ω.

Question 43Physics – Laws of Motion, Optics, Electricity and Magnetism

A 60 W bulb and a 100 W bulb, both rated for 220 V, are connected in series across a 220 V supply. Which bulb glows brighter?

  1. Neither bulb glows
  2. Both glow equally brightly
  3. The 60 W bulb Correct answer.
  4. The 100 W bulb

Explanation

In series the same current flows through both bulbs, so brightness depends on resistance, since P = I²R. The 60 W bulb has the higher resistance (R = V²/P), so it dissipates more power and glows brighter.

Question 44Physics – Laws of Motion, Optics, Electricity and Magnetism

In a household wiring circuit, the fuse is connected in the:

  1. Live wire, in parallel with the appliances
  2. Neutral wire, in parallel with the appliances
  3. Live wire, in series with the appliances Correct answer.
  4. Earth wire, in series with the appliances

Explanation

A fuse must carry the whole current of the circuit to melt and break it during overload, so it is connected in series. It is placed in the live wire so that the circuit is disconnected from the high potential when it blows.

Question 45Physics – Laws of Motion, Optics, Electricity and Magnetism

Two cells of emf 2 V each and internal resistance 0.5 Ω each are connected in parallel across a 3 Ω resistor. What is the current through the resistor?

  1. 0.57 A Correct answer.
  2. 0.8 A
  3. 1.33 A
  4. 0.4 A

Explanation

For identical cells in parallel, the emf stays 2 V and the internal resistance becomes 0.5/2 = 0.25 Ω. The total resistance is 3 + 0.25 = 3.25 Ω, so I = 2/3.25 ≈ 0.57 A.

Question 46Physics – Laws of Motion, Optics, Electricity and Magnetism

The magnetic field lines around a long straight current-carrying conductor are:

  1. Concentric circles in a plane perpendicular to the conductor Correct answer.
  2. Radial lines pointing away from the conductor
  3. Straight lines parallel to the conductor
  4. Straight lines perpendicular to the conductor

Explanation

By the right-hand grip rule, the magnetic field around a straight conductor forms closed circular loops centred on the wire. These circles lie in planes perpendicular to the length of the conductor, with their direction given by the thumb of the right hand.

Question 47Physics – Laws of Motion, Optics, Electricity and Magnetism

A current-carrying conductor placed in a magnetic field experiences maximum force when the angle between the conductor and the field is:

  1. 90° Correct answer.
  2. 45°
  3. 180°
  4. 0°

Explanation

The force on a conductor is F = BIl sin θ, where θ is the angle between the conductor and the field. Since sin θ is greatest at 90°, the force is maximum when the conductor is perpendicular to the field.

Question 48Physics – Laws of Motion, Optics, Electricity and Magnetism

In an electric motor, the split-ring commutator is used to:

  1. Reverse the direction of current in the coil after every half rotation Correct answer.
  2. Convert alternating current into direct current for the supply
  3. Produce a steady magnetic field
  4. Increase the resistance of the coil

Explanation

The coil of a motor tends to stop after half a rotation because the forces would then reverse its motion. The split-ring commutator reverses the current in the coil every half rotation so that the torque continues in the same direction.

Question 49Physics – Laws of Motion, Optics, Electricity and Magnetism

Which device works on the principle of electromagnetic induction?

  1. AC generator Correct answer.
  2. Electric heater
  3. Moving-coil galvanometer
  4. Fuse

Explanation

An AC generator produces emf by rotating a coil in a magnetic field, so the magnetic flux linked with the coil changes continuously. This changing flux inducing an emf is electromagnetic induction.

Question 50Physics – Laws of Motion, Optics, Electricity and Magnetism

A transformer is used to step up an alternating voltage from 110 V to 440 V. If the secondary current is 2 A, what is the primary current, assuming an ideal transformer?

  1. 2 A
  2. 4 A
  3. 0.5 A
  4. 8 A Correct answer.

Explanation

For an ideal transformer, input power equals output power, so VpIp = VsIs. Thus Ip = (440 × 2)/110 = 8 A. A step-up transformer raises voltage but lowers current in the same ratio.