اردو

Home / Practice / Electricity and magnetism / Worksheet

Practise online

Electricity and magnetism

Written by Dr. Hamza Farooq (Physics)

MDCAT · Physics · 10 questions

Name: ____________________   Date: ____________

  1. A 12 V battery is connected across a 4 ohm resistor. What current flows?

    • A 8 A
    • B 0.33 A
    • C 3 A
    • D 48 A

  2. Resistors of 2, 3 and 5 ohms are connected in series. What is the total resistance?

    • A 0.97 ohm
    • B 30 ohm
    • C 10 ohm
    • D 3.3 ohm

  3. A 6 ohm and a 3 ohm resistor are connected in parallel. What is the equivalent resistance?

    • A 2 ohm
    • B 18 ohm
    • C 9 ohm
    • D 4.5 ohm

  4. An appliance on 220 V draws 2 A. What is its power?

    • A 110 W
    • B 222 W
    • C 440 W
    • D 880 W

  5. The SI unit of capacitance is the:

    • A Farad
    • B Weber
    • C Tesla
    • D Henry

  6. The magnetic force on a moving charge is always:

    • A Opposite to its velocity
    • B Perpendicular to its velocity
    • C Parallel to its velocity
    • D Zero

  7. A step-up transformer has:

    • A More turns in the primary coil
    • B More turns in the secondary coil
    • C Equal turns in both coils
    • D Only one coil

  8. Faraday's law of induction states that the induced emf is proportional to:

    • A The resistance of the coil
    • B The charge on the coil
    • C The magnetic flux
    • D The rate of change of magnetic flux

  9. How much electrical energy does a 2 kW heater use in 3 hours?

    • A 6 kWh
    • B 23 kWh
    • C 1.5 kWh
    • D 5 kWh

  10. Lenz's law is a consequence of the conservation of:

    • A Charge
    • B Energy
    • C Mass
    • D Momentum

Answer key

1. C, 2. C, 3. A, 4. C, 5. A, 6. B, 7. B, 8. D, 9. A, 10. B

  1. By Ohm's law, I = V / R = 12 / 4 = 3 A.

  2. In series the resistances add: 2 + 3 + 5 = 10 ohm.

  3. 1/R = 1/6 + 1/3 = 3/6, so R = 2 ohm.

  4. P = VI = 220 x 2 = 440 W.

  5. Capacitance is measured in farads. The henry is for inductance, the tesla for magnetic field and the weber for magnetic flux.

  6. F = qvB sin θ acts at right angles to the velocity, so the force changes the direction of motion but not the speed.

  7. The output voltage is larger when the secondary has more turns than the primary.

  8. The induced emf depends on how fast the flux linked with the circuit changes.

  9. Energy = power x time = 2 kW x 3 h = 6 kWh.

  10. The induced current opposes the change that causes it. If it did not, energy would appear from nothing.