Unit 19: Electromagnetism

1

Electromagnetic induction occurs when:

A Current flows steadily B Magnetic field is constant C Magnetic flux changes D Circuit is open

2

The screen of a CRO is coated with:

A Aluminum B Zinc sulphide C Copper D Carbon

3

The main principle of an electric motor is:

A Electrostatics B Magnetic induction C Force on current carrying conductor D Heating effect of current

4

The strength of magnetic field around a current carrying wire depends on:

A Length of wire B Material of wire C Current through the wire D Color of wire

5

Lenz’s law is a consequence of conservation of:

A Charge B Energy C Mass D Momentum

6

A solenoid produces a magnetic field similar to that of a:

A Bar magnet B Ring magnet C Horseshoe magnet D Circular magnet

7

CRO is mainly used to observe:

A Resistance B Voltage waveforms C Current directly D Power

8

The unit of magnetic field strength is:

A Newton B Tesla C Volt D Ampere

9

The induced current flows in such a direction as to oppose the change producing it according to:

A Ohm’s law B Faraday’s law C Lenz’s law D Coulomb’s law

10

Increasing the number of turns in a coil will:

A Decrease induced emf B Have no effect C Increase induced emf D Stop induction

11

The working principle of electric generator is:

A Heating effect B Chemical effect C Electromagnetic induction D Electrostatic force

12

When the direction of current is reversed, the direction of force:

A Remains same B Becomes zero C Is reversed D Becomes maximum

13

The magnetic field around a straight current carrying conductor consists of:

A Straight lines B Circular lines C Elliptical lines D Random lines

14

The vertical deflection plates in a CRO control:

A Time base B Brightness C Vertical deflection of beam D Focus

15

Inside a long solenoid, the magnetic field is:

A Zero B Weak and varying C Strong and uniform D Random

16

Which quantity remains constant in an ideal transformer?

A Voltage B Current C Power D Resistance

17

Which scientist discovered the magnetic effect of electric current?

A Michael Faraday B Hans Christian Oersted C James Clerk Maxwell D Isaac Newton

18

Which device converts mechanical energy into electrical energy?

A Motor B Transformer C Generator D Battery

19

The split ring in a DC motor is also called:

A Armature B Commutator C Field magnet D Slip ring

20

A current carrying coil placed in a magnetic field experiences:

A No force B A torque C Only attraction D Only repulsion

21

Which law gives magnitude of induced emf?

A Ohm’s law B Faraday’s law C Lenz’s law D Kirchhoff’s law

22

The force acting on a moving electron in a magnetic field is:

A Electric force B Magnetic force C Gravitational force D Nuclear force

23

The rule used to find direction of force on a conductor is:

A Right hand thumb rule B Fleming’s left hand rule C Fleming’s right hand rule D Maxwell’s rule

24

A transformer works only with:

A DC supply B AC supply C Battery D Solar cell

25

The magnetic field of Earth is similar to that of:

A A straight wire B A solenoid C A bar magnet D An electric motor