Current Electricity and Electromagnetism Quiz

A light bar magnet is suspended near a current carrying wire as shown below. What will happen to the light bar magnet?

1. It will rotate in the clockwise direction
2. It will rotate in an anti-clockwise direction
3. It will move to the right side
4. It will move to the left side

Answer: (a) It will rotate in the clockwise direction

When two unknown resistences are connected in series and in parallel, their equivalent resistences are 9 Ω and 2 Ω respectively. What are the unknown resistances?

1. 3, 2
2. 6, 3
3. 2, 8
4. 6, 2

Answer: (b) 6, 3

A bar magnet is rotated on a shaft near to a coil which is connected to a resistor of resistance R as shown in the figure. Which of the following changes does not increase the induced current in the coil?

1. Moving the magnet closer to the coil.
2. Turning the magnet in the opposite direction at the same speed.
3. Turning the magnet in the opposite direction at a greater speed.
4. Using a coil with more turns.

Answer: (b) Turning the magnet in the opposite direction at the same speed.

A current of 0.75 A is passing through a wire of resistance 6 Ω. Find the potential difference across the wire.

1. 0.125 V
2. 4 V
3. 4.5 V
4. 12.5 V

Answer: (c) 4.5 V

Three wires—X, Y, and Z—are made of the same material and have the same length. Their cross-sectional areas are in the ratio 1:2:3. What will be the ratio of their resistances?

1. 6:3:2
2. 3:2:1
3. 1:4:9
4. 9:4:1

Answer: (a) 6:3:2

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

1. Increase the speed of rotation
2. Reduce energy loss due to heat
3. Strengthen the magnetic field
4. Reverse the direction of current in the coil

Answer: (d) Reverse the direction of current in the coil

Which factor does NOT affect the magnitude of the induced electromotive force (EMF)?

1. Speed of relative motion between conductor and magnet
2. Strength of the magnetic field
3. Length of the conductor in the field
4. Material of the conductor

Answer: (d) Material of the conductor

A 60 W bulb (240 V) and a 100 W bulb (240 V) are connected in series to a 240 V supply. Which statement is correct?

1. Both bulbs glow equally bright
2. The 100 W bulb glows brighter
3. The 60 W bulb glows brighter
4. The bulbs do not glow at all

Answer: (c) The 60 W bulb glows brighter

A cylindrical iron core is placed inside a solenoid, increasing its magnetic field strength. If the iron core is replaced with copper, what will happen?

1. The magnetic field will remain unchanged.
2. The magnetic field will increase slightly
3. The magnetic field will decrease
4. The copper will become permanently magnetized.

Answer: (c) The magnetic field will decrease

The image below shows iron filings forming a circular pattern around a vertical current-carrying wire. If the current direction is upwards, in which direction will the magnetic field lines be?

1. Clockwise when viewed from above
2. Parallel to the wire, moving in a straight line
3. Radial, moving outward from the wire
4. Anticlockwise when viewed from above

Answer: (d) Anticlockwise when viewed from above