Objective Type Question and Answers On Class 12 Physics Chapter 4

1 The radius of the trajectory of a charged particle in a uniform magnetic field is proportional to the:

A charge on the particle

B energy of the particle

C momentum of the particle

D all the above

Answer:momentum of the particle

2 10 eV electron is circulating in a plane at right angle to a uniform field of magnetic induction 10-1 Wb/m² (1G). The orbital radius of electron is:

A 12 cm

B 16 cm

C 11 cm

D 18 cm

View Answer

Answer:11 cm

3 Earth’s magnetism was discovered by:

A Gauss

B Oersted

C Ampere

D Gilbert

View Answer

Answer:Gilbert

4 Isoclinic lines are the lines joining places with :

A equal dip

B equal declination

C equal dip and declination

D None of these

View Answer

Answer:equal dip

5 When charged particle enters-a uniform magnetic field, its K.E.:

A remains constant

B increases

C decreases

D becomes zero

View Answer

Answer:remains constant

6 Which of the following is not a unit of magnetic induction?

A gauss

B tesla

C oersted

D weber/metre²

View Answer

Answer:oersted

7 A current carrying power line carries current from west to east. Then the direction of the magnetic field 2 m above it is :

A west to east

B south to north

C north to south

D None of these

View Answer

Answer:north to south

8 What happens to the magnetic field at the centre of a circular current carrying coil if we double the radius of the coil keeping the current unchanged?

A halved

B doubled

C quadrupled

D remains unchanged

View Answer

Answer:halved

9 What is the angle of dip at the magnetic poles ?

A 30°

B 0°

C 45°

D None of these

View Answer

Answer:None of these

10 A wire of length 2 metre carries a current 1 ampere, is bent to form a circle. The magnetic moment of the coil is :

A 2π

B π/2

C π/4

D 1/π

View Answer

Answer:1/π

11 The force between two parallel current carrying conductors is F. If the current in each conductor is doubled, then the force between them becomes :

A 4F

B 2F

C F

D F/4

View Answer

Answer:4F

12 The strength of the magnetic field around an infinite current carrying conductor is :

A same everywhere

B inversely proportional to the distance

C directly proportional to the distance

D None of these

View Answer

Answer:inversely proportional to the distance

13 To convert galvanometer into voltmeter one should connect :

A high resistance in series with galvanometer

B low resistance in series with galvanometer

C high resistance in parallel with galvanometer

D low resistance in parallel with galvanometer

View Answer

Answer:high resistance in series with galvanometer

14 The magnetic field of a given length of a ware for single turn coil at its centre is B. Then.its value for two turns of coil will be :

A B/4

B B/2

C 4B

D 2B

View Answer

Answer:4B

15 The magnetic field produced by an / meter long straight (x cry thin) current (I) carry ing conductor at any point on itself is :

A zero

B infinite

C µ0^l/4πl

D µ0^l/2πl

View Answer

Answer:zero

16 When we double the radius of a coil keeping the current through it unchanged, what happens to the magnetic field directed along its axis at far off points?

A halved

B doubled

C quadrupled

D remains unchanged

View Answer