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Kerala SSLC Physics study materials
Kerala SSLC Physics study resources

Kerala SSLC Physics practice questions

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Question 1Effects of Electric Current

In a household electric circuit in Kerala, the wire that is maintained at nearly zero potential and provides the return path for current is called the:

  1. fuse wire
  2. neutral wire Correct answer.
  3. earth wire
  4. live wire

Explanation

The neutral wire completes the circuit and is kept at approximately earth potential, so touching it is normally safe. The live wire carries the high potential, while the earth wire is a safety conductor connected to the ground.

Question 2Effects of Electric Current

The standard frequency of the alternating current supplied to domestic consumers in India is:

  1. 50 Hz Correct answer.
  2. 60 Hz
  3. 230 Hz
  4. 100 Hz

Explanation

Indian domestic supply alternates at 50 cycles per second, that is 50 Hz, with a declared voltage of about 230 V. The frequency is fixed by the generating and distribution system, independent of the load.

Question 3Effects of Electric Current

The heating element of an electric iron is made of an alloy such as nichrome mainly because the alloy has:

  1. a low melting point
  2. high resistivity and a high melting point Correct answer.
  3. negligible resistance at high temperature
  4. very low resistivity

Explanation

A heating element must convert electrical energy into heat strongly and must not melt at red heat. Nichrome offers high resistivity, so a short length gives sufficient resistance, and it withstands high temperatures without oxidising quickly.

Question 4Effects of Electric Current

An electric bulb is marked 60 W, 230 V. The resistance of its filament while glowing is about:

  1. 880 ohm
  2. 8.8 ohm
  3. 88 ohm Correct answer.
  4. 0.26 ohm

Explanation

From P = V²/R, the resistance is R = V²/P = (230)²/60, which is about 880 ohm. This is the resistance at operating temperature; the cold filament has a much lower resistance.

Question 5Effects of Electric Current

The direction of the magnetic field around a straight current-carrying conductor is given by:

  1. Fleming's left-hand rule
  2. Lenz's law
  3. the right-hand thumb rule Correct answer.
  4. Fleming's right-hand rule

Explanation

The right-hand thumb rule states that if the thumb points along the current, the curled fingers give the direction of the magnetic field lines around the conductor. The other rules relate to force on a conductor or induced current.

Question 6Effects of Electric Current

The magnetic field is strongest in a current-carrying solenoid:

  1. near the ends of the solenoid
  2. at a point far outside the solenoid
  3. at the outer curved surface
  4. inside the solenoid near its centre Correct answer.

Explanation

Inside a solenoid the field lines are parallel and closely packed, giving a nearly uniform and strong field near the centre. Outside, the field lines spread out and the field is weak.

Question 7Effects of Electric Current

The safety device connected in series in the live wire of a domestic circuit that melts and breaks the circuit on excess current is the:

  1. fuse Correct answer.
  2. earth wire
  3. ammeter
  4. rheostat

Explanation

A fuse contains a thin wire of low melting point that melts when the current exceeds the rated value, protecting appliances and wiring. It is connected in the live wire so that the circuit is broken before damage occurs.

Question 8Effects of Electric Current

The unit of electric power used in household electricity bills in Kerala is the:

  1. kilowatt-hour Correct answer.
  2. watt
  3. ampere
  4. joule

Explanation

Electrical energy consumed is measured in kilowatt-hours, where one kilowatt-hour equals the energy used by a 1000 W appliance running for one hour. Billing is based on this energy unit, commonly called one unit.

Question 9Effects of Electric Current

A current of 2 A flows through a conductor of resistance 15 ohm for 5 minutes. The heat produced is:

  1. 18000 J Correct answer.
  2. 9000 J
  3. 1800 J
  4. 150 J

Explanation

Using H = I²Rt with t = 5 × 60 = 300 s gives H = 4 × 15 × 300 = 18000 J. The time must be converted to seconds before substitution.

Question 10Effects of Electric Current

Two resistors of 6 ohm and 3 ohm are connected in parallel across a 6 V battery. The total current drawn from the battery is:

  1. 3 A Correct answer.
  2. 2 A
  3. 0.67 A
  4. 1 A

Explanation

The parallel combination gives 1/R = 1/6 + 1/3 = 1/2, so R = 2 ohm, and I = V/R = 6/2 = 3 A. Alternatively, the branch currents 1 A and 2 A add to 3 A.

Question 11Effects of Electric Current

An electric heater of 1500 W is used for 4 hours daily. The energy consumed in 30 days is:

  1. 18 kWh
  2. 6 kWh
  3. 180 kWh Correct answer.
  4. 1800 kWh

Explanation

Daily energy is 1.5 kW × 4 h = 6 kWh, and for 30 days this becomes 6 × 30 = 180 kWh. Power in kilowatts multiplied by time in hours gives kilowatt-hours directly.

Question 12Effects of Electric Current

When the current through a conductor is doubled while its resistance is kept constant, the heat produced in a given time becomes:

  1. unchanged
  2. doubled
  3. four times Correct answer.
  4. halved

Explanation

Joule's law gives H = I²Rt, so heat is proportional to the square of the current. Doubling the current therefore multiplies the heat by four when R and t are fixed.

Question 13Effects of Electric Current

A magnetic compass needle placed near a current-carrying wire deflects. This observation was first explained by:

  1. Joule
  2. Ohm
  3. Faraday
  4. Oersted Correct answer.

Explanation

Oersted discovered in 1820 that a current-carrying conductor produces a magnetic field that deflects a nearby compass needle. This established the magnetic effect of electric current.

Question 14Effects of Electric Current

The strength of the magnetic field produced by a solenoid can be increased by:

  1. winding the coil on a plastic core instead of iron
  2. decreasing the number of turns
  3. increasing the current through it Correct answer.
  4. removing the soft iron core

Explanation

The field of a solenoid increases with the current and with the number of turns per unit length. Inserting a soft iron core also strengthens it greatly by magnetisation.

Question 15Effects of Electric Current

In an electric motor, the function of the split ring commutator is to:

  1. convert alternating current into direct current for the coil
  2. increase the resistance of the coil
  3. reverse the direction of current in the coil after every half rotation Correct answer.
  4. reduce the strength of the magnetic field

Explanation

The commutator reverses the current in the coil each time it passes the vertical position, so the torque continues in the same direction and the coil keeps rotating. Without it, the coil would oscillate and stop.

Question 16Effects of Electric Current

The direction of the force on a current-carrying conductor placed in a magnetic field is obtained using:

  1. Fleming's left-hand rule Correct answer.
  2. Fleming's right-hand rule
  3. the right-hand thumb rule
  4. Kirchhoff's rule

Explanation

Fleming's left-hand rule relates the forefinger (field), middle finger (current), and thumb (force) for a conductor in a magnetic field. It is applied to motors and to moving charges in fields.

Question 17Effects of Electric Current

The earth wire in a domestic circuit is connected to:

  1. the metal body of the appliance and to the ground Correct answer.
  2. the fuse in the live wire
  3. the neutral wire only
  4. the live wire at the switch

Explanation

The earth wire connects the metallic body of an appliance to a metal plate buried in the ground. If the live wire touches the body, current flows safely to the earth, preventing a severe shock.

Question 18Effects of Electric Current

An electric bulb marked 100 W, 230 V and another marked 60 W, 230 V are connected in series across a 230 V supply. Which bulb glows brighter?

  1. both equally
  2. the 100 W bulb
  3. neither glows
  4. the 60 W bulb Correct answer.

Explanation

In series the current is the same through both, and the heat produced depends on I²R. The 60 W bulb has the greater resistance (V²/P), so it dissipates more power and glows brighter.

Question 19Effects of Electric Current

The resistance of a conductor of length L and area of cross-section A is R. If the length is doubled and the area is halved, the new resistance is:

  1. 2R
  2. R/4
  3. R
  4. 4R Correct answer.

Explanation

Resistance is given by R = ρL/A, so it is directly proportional to length and inversely proportional to area. Doubling the length doubles R, and halving the area doubles it again, giving 4R.

Question 20Effects of Electric Current

In a domestic wiring system, appliances are connected in parallel mainly because:

  1. each appliance then gets the full supply voltage and can be switched independently Correct answer.
  2. the current drawn from the supply decreases
  3. a fault in one appliance breaks the whole circuit
  4. the total resistance of the circuit increases

Explanation

In a parallel connection every appliance receives the same supply voltage, which is necessary for correct operation, and each branch can be switched on or off without affecting the others. The total resistance falls and the total current rises as more appliances are added.

Question 21Effects of Electric Current

A 2 kW geyser draws current from a 230 V supply. The current drawn is approximately:

  1. 46 A
  2. 87 A
  3. 0.87 A
  4. 8.7 A Correct answer.

Explanation

Using P = VI, the current is I = P/V = 2000/230, which is about 8.7 A. The fuse and wiring must be rated above this value.

Question 22Effects of Electric Current

A wire carries a current towards the north. At a point directly above the wire, the magnetic field lines are directed:

  1. towards the north
  2. towards the south
  3. towards the west
  4. towards the east Correct answer.

Explanation

With the thumb of the right hand pointing north along the current, the fingers curl around the wire. At a point above the wire the curl points towards the east.

Question 23Effects of Electric Current

A 60 W and a 100 W bulb, both rated 230 V, are connected in series to a 230 V supply. The ratio of the power consumed by the 60 W bulb to that consumed by the 100 W bulb is:

  1. 9 : 25
  2. 5 : 3 Correct answer.
  3. 3 : 5
  4. 25 : 9

Explanation

Their resistances are in the ratio R60 : R100 = 100 : 60 = 5 : 3. In series the current is common, so power ratio equals resistance ratio, 5 : 3, and the 60 W bulb consumes more.

Question 24Effects of Electric Current

In an electric motor, the coil is in a position where the plane of the coil is perpendicular to the magnetic field. The torque on the coil at that instant is:

  1. maximum
  2. half the maximum
  3. independent of the field
  4. zero Correct answer.

Explanation

Torque depends on the component of the magnetic force that acts perpendicular to the coil plane, which is greatest when the coil plane is parallel to the field. When the plane is perpendicular to the field, the forces act in the plane of the coil and produce no turning effect, so torque is zero.

Question 25Effects of Electric Current

A fuse of 5 A rating is used in a circuit that has a 1500 W heater operating at 230 V. Which statement is correct?

  1. The fuse rating is unrelated to the appliance current
  2. The fuse is unsuitable because the current of about 6.5 A exceeds its rating Correct answer.
  3. The fuse is suitable because the current is only about 0.65 A
  4. The fuse is suitable because the current is about 6.5 A

Explanation

The heater current is I = 1500/230, about 6.5 A, which is greater than the 5 A rating. The fuse wire would melt and interrupt the circuit during normal operation, so a fuse rated above 6.5 A is needed.

Question 26Effects of Electric Current

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

  1. straight lines perpendicular to the conductor
  2. concentric circles centred on the conductor Correct answer.
  3. straight lines parallel to the conductor
  4. radial lines spreading outward from the conductor

Explanation

According to the right-hand grip rule, the magnetic field lines around a straight conductor form concentric circles in a plane perpendicular to the conductor. The direction of the field is given by the tangent to these circles. This pattern was established by Oersted's observation that a compass needle deflects near a current-carrying wire.

Question 27Effects of Electric Current

The magnitude of the magnetic field produced by a long straight wire at a distance r from it is B. If the current is doubled and the distance is also doubled, the new magnetic field at that distance is:

  1. B/2
  2. B Correct answer.
  3. 2B
  4. 4B

Explanation

The magnetic field due to a long straight conductor is directly proportional to the current and inversely proportional to the distance from the wire. Doubling both the current and the distance changes the field by the factor (2)/(2) = 1, so the field remains B. This follows from the relation B = μ₀I/(2πr).

Question 28Effects of Electric Current

A copper wire of length 0.5 m carrying a current of 2 A is placed perpendicular to a uniform magnetic field of 0.4 T. The magnitude of the force acting on the wire is:

  1. 1.6 N
  2. 0.2 N
  3. 0.8 N
  4. 0.4 N Correct answer.

Explanation

The force on a current-carrying conductor in a magnetic field is given by F = B I L sinθ. Here θ = 90°, so sinθ = 1, and F = 0.4 × 2 × 0.5 = 0.4 N. The direction of the force is given by Fleming's left-hand rule.

Question 29Effects of Electric Current

A domestic electric circuit uses a fuse of 10 A rating. An electric iron of 2000 W is connected to a 230 V supply. Which statement about the fuse is correct?

  1. The fuse will melt because the current exceeds 10 A Correct answer.
  2. The fuse rating is too high for the iron, so it will not protect the circuit
  3. The fuse will not melt because the current is less than 10 A
  4. The fuse will melt only if another appliance is switched on

Explanation

The current drawn by the iron is I = P/V = 2000/230 ≈ 8.7 A, which is less than the 10 A rating of the fuse. Therefore the fuse will not melt under normal operation. A fuse melts only when the current exceeds its rated value.

Question 30Effects of Electric Current

The magnetic field inside a current-carrying solenoid is uniform and its strength can be increased by:

  1. increasing the number of turns per unit length Correct answer.
  2. decreasing the current through the solenoid
  3. winding the solenoid on a wooden core instead of an iron core
  4. removing the soft iron core from the solenoid

Explanation

The magnetic field inside a solenoid is directly proportional to the number of turns per unit length and to the current. Increasing the turns per unit length therefore increases the field strength. Inserting a soft iron core also increases the field, so removing it or using a wooden core would weaken the field.

Question 31Magnetic Effect of Electric Current

A long straight conductor carries a steady current. The magnetic field lines produced around it in a plane perpendicular to the wire are best described as:

  1. Radial lines spreading outward from the wire
  2. Straight lines parallel to the wire
  3. Straight lines perpendicular to the wire
  4. Concentric circles centred on the wire Correct answer.

Explanation

The field of a straight current-carrying conductor forms closed circular loops around the wire, with the wire at the centre of each circle. Their direction is given by the right-hand thumb rule: thumb along the current, curled fingers show the field.

Question 32Magnetic Effect of Electric Current

The direction of the magnetic field at a point near a current-carrying straight conductor is determined using:

  1. The right-hand thumb rule Correct answer.
  2. Lenz's law
  3. Fleming's left-hand rule
  4. Fleming's right-hand rule

Explanation

The right-hand thumb rule (Maxwell's corkscrew rule) relates current direction to field direction around a conductor. The thumb points along the current and the curled fingers give the field direction.

Question 33Magnetic Effect of Electric Current

A bar magnet is placed with its north pole facing a coil. On looking from the magnet side, the coil face behaves as a north pole. The current in the coil, as seen from that side, is:

  1. Alternating
  2. Anticlockwise Correct answer.
  3. Zero
  4. Clockwise

Explanation

Looking at a coil face that acts as a north pole, the current appears anticlockwise. This follows from the clock face rule, which links the polarity of a current-carrying loop to its current direction.

Question 34Magnetic Effect of Electric Current

The magnetic field inside a long solenoid carrying a steady current is:

  1. Uniform and parallel to the axis Correct answer.
  2. Directed radially outward from the axis
  3. Zero everywhere inside
  4. Strongest near the windings and zero on the axis

Explanation

Inside a long solenoid the field lines are parallel straight lines, so the field is uniform in magnitude and direction along the axis. Outside, the pattern resembles that of a bar magnet.

Question 35Magnetic Effect of Electric Current

An electromagnet differs from a permanent magnet mainly because its magnetism:

  1. Exists only when current flows through its coil Correct answer.
  2. Is weaker than that of any permanent magnet
  3. Cannot attract iron filings
  4. Reverses only when the coil is heated

Explanation

An electromagnet is a soft-iron core magnetised by current in a surrounding coil. When the current stops, the core loses most of its magnetism, so the magnetism can be switched on and off.

Question 36Magnetic Effect of Electric Current

The strength of the magnetic field at the centre of a circular coil is increased by:

  1. Increasing the number of turns of the coil Correct answer.
  2. Increasing the radius of the coil
  3. Placing the coil in a vacuum
  4. Decreasing the current in the coil

Explanation

The field at the centre of a circular coil is proportional to the current and to the number of turns, and inversely proportional to the radius. Adding turns therefore strengthens the field.

Question 37Magnetic Effect of Electric Current

Fleming's left-hand rule is used to find the direction of:

  1. Force on a current-carrying conductor in a magnetic field Correct answer.
  2. Induced current in a coil
  3. Magnetic field around a straight wire
  4. Polarity of an electromagnet

Explanation

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

Question 38Magnetic Effect of Electric Current

A current-carrying coil is placed in a magnetic field. It experiences a torque that tends to:

  1. Align the plane of the coil parallel to the field
  2. Align the magnetic axis of the coil along the field Correct answer.
  3. Push the coil out of the field without rotating it
  4. Reduce the current in the coil to zero

Explanation

The forces on opposite sides of the coil form a couple that rotates it until its magnetic axis lies along the field. This is the principle of the moving-coil galvanometer and the electric motor.

Question 39Magnetic Effect of Electric Current

A straight wire carrying current towards the observer is placed in the plane of the page. A compass needle placed just below the wire, in the plane of the page, deflects:

  1. Away from the observer
  2. Towards the observer
  3. Towards the left of the page
  4. Towards the right of the page Correct answer.

Explanation

With the current coming out of the page, the field lines circle anticlockwise as seen by the observer. At a point below the wire, the tangent to such a circle points to the observer's right.

Question 40Magnetic Effect of Electric Current

Two long parallel wires carry currents in the same direction. The force between them is:

  1. Repulsive
  2. Attractive Correct answer.
  3. Attractive only if the currents are equal
  4. Zero because the fields cancel

Explanation

Each wire lies in the magnetic field of the other, and the resulting force pulls them together when the currents are parallel. Antiparallel currents give a repulsive force.

Question 41Magnetic Effect of Electric Current

The magnetic field at a point due to a long straight wire is B when the current is I. If the current is doubled and the distance from the wire is also doubled, the new field is:

  1. B/2
  2. 2B
  3. B Correct answer.
  4. 4B

Explanation

The field of a long straight wire is proportional to current and inversely proportional to distance. Doubling both multiplies the field by 2/2, so it stays equal to B.

Question 42Magnetic Effect of Electric Current

A soft-iron core is inserted into a solenoid carrying a steady current. The magnetic field of the solenoid:

  1. Increases greatly Correct answer.
  2. Reverses direction
  3. Decreases slightly
  4. Becomes zero

Explanation

Soft iron is easily magnetised and its own magnetism adds to the field of the coil, so the field becomes much stronger. This is why electromagnets use soft-iron cores.

Question 43Magnetic Effect of Electric Current

A positively charged particle moves horizontally towards the east in a magnetic field directed vertically upward. The magnetic force on it acts:

  1. Vertically upward
  2. Horizontally towards the south Correct answer.
  3. Horizontally towards the north
  4. Vertically downward

Explanation

For a positive charge, the force is perpendicular to both velocity and field, given by the left-hand rule with current along the velocity. East crossed with upward gives a force towards the south.

Question 44Magnetic Effect of Electric Current

A current-carrying conductor placed parallel to a uniform magnetic field experiences:

  1. A force opposite to the current
  2. Zero force Correct answer.
  3. A force along the field
  4. Maximum force

Explanation

The magnetic force on a conductor is greatest when the conductor is perpendicular to the field and falls to zero when it is parallel. With no perpendicular component, no force acts.

Question 45Magnetic Effect of Electric Current

In a moving-coil galvanometer, a cylindrical soft-iron core is placed between the pole pieces mainly to:

  1. Reduce the number of turns needed to zero
  2. Prevent the coil from rotating
  3. Increase the resistance of the coil
  4. Make the magnetic field radial in the coil's region Correct answer.

Explanation

The soft-iron cylinder concentrates the field and makes it radial, so the coil's plane is always parallel to the field. This gives a uniform torque and a linear scale.

Question 46Magnetic Effect of Electric Current

The magnetic field inside a solenoid of N turns, length L and current I is proportional to:

  1. N/(L·I)
  2. N·I/L Correct answer.
  3. N·L·I
  4. L/(N·I)

Explanation

For a long solenoid, the field is proportional to the number of turns per unit length and to the current. Hence it varies as N·I/L, so more turns per metre or more current gives a stronger field.

Question 47Magnetic Effect of Electric Current

An electric motor's coil continues to rotate past the vertical position because:

  1. The brushes stop touching the commutator permanently
  2. The current in the coil is reversed by the commutator at that instant Correct answer.
  3. The coil loses all its momentum at that instant
  4. The magnetic field disappears at that instant

Explanation

At the vertical position the couple on the coil would reverse and stop rotation. The split-ring commutator reverses the current at that moment, so the torque keeps the coil turning the same way.

Question 48Magnetic Effect of Electric Current

A wire of a given length is bent into a circular loop of one turn and then into a coil of two turns using the same total length. The field at the centre, for the same current, becomes:

  1. Half
  2. Four times Correct answer.
  3. Twice
  4. One quarter

Explanation

With two turns from the same wire, the radius is halved and the number of turns is doubled. The field varies as N/r, so doubling N and halving r multiplies the field by four.

Question 49Magnetic Effect of Electric Current

A compass needle placed at the centre of a circular coil lies along the coil's axis when current flows. If the current is reversed, the needle:

  1. Turns through 180° Correct answer.
  2. Turns through 90° and stays there
  3. Does not move
  4. Vibrates without settling

Explanation

Reversing the current reverses the direction of the magnetic field at the centre. The needle therefore rotates through 180° to align with the new field direction.

Question 50Magnetic Effect of Electric Current

A current-carrying straight conductor is placed in a magnetic field directed into the page, with the current flowing towards the top of the page. The force on the conductor acts:

  1. Towards the right of the page
  2. Into the page
  3. Towards the left of the page Correct answer.
  4. Towards the top of the page

Explanation

Using Fleming's left-hand rule, the forefinger points into the page and the middle finger points upward. The thumb then points to the left, which is the force direction.