#### Magnetism and Magnetic Effects of Electric Current One Mark Questions with Answer

12th Standard EM

Reg.No. :
•
•
•
•
•
•

Physics

Time : 00:45:00 Hrs
Total Marks : 25
25 x 1 = 25
1. The most suitable metal for permanent magnet is

(a)

copper

(b)

aluminium

(c)

steel

(d)

iron

2. Direction of magnetic force on a positive charge moving in a magnetic field is given by

(a)

thumb rule

(b)

left hand rule

(c)

right hand rule

(d)

cork screw rule

3. Lorentz force generally refers to force experienced by a charge due to combined action of

(a)

magnetic fields

(b)

electric fields

(c)

electric, magnetic & gravitational fields

(d)

electric and magnetic fields

4. Two thin long parallel wires separated by a distancea' are carrying current I amp each. The magnitude of the force per unit length excited by one wire on the other is

(a)

$\frac { { \mu }_{ 0 }{ I }^{ 2 } }{ a^{ 2 } }$

(b)

$\frac { { \mu }_{ 0 }{ I }^{ 2 } }{ 2\pi a }$

(c)

$\frac { { \mu }_{ 0 }{ I } }{ 2\pi a }$

(d)

$\frac { { \mu }_{ 0 }{ I } }{ 2\pi a^{ 2 } }$

5. At a given place the horizontal component of earth's field is 0.2 x 10-4 Tesla. If a vertical wire carries a current of 30A upward, what is the magnitude and direction of the force on 1m of wire?

(a)

6 East to West

(b)

6 x 10-2 East to West

(c)

6 x 10-3 East to West

(d)

6 x 10-4 East to West

6. Which one of the following pair of particles move with same velocity along the same circular path in a uniform magnetic field?

(a)

electron, proton

(b)

proton, deutron

(c)

proton, alpha particle

(d)

deutron, alpha particle

7. In a T.G. experiment, for two different values of current, the deflections are 45° and 30° respectively, then the ratio of the current is

(a)

2 : 3

(b)

3 : 2

(c)

$\sqrt{3}$ : 1

(d)

1 : $\sqrt{3}$

8. The Tangent Galvanometer is more sensitive for this angle of deflection

(a)

(b)

(c)

(d)

9. The magnitude and direction of magnetic Lorentz force

(a)

$\vec { F } =\vec { v } \times \vec { B }$

(b)

$\vec { F } =q/(\vec { v } \times \vec { B } )$

(c)

$\vec { F } =q(\vec { v } \times \vec { B } )$

(d)

$\vec { F } =v(\vec { v } \times \vec { B } )$

10. The angular. momentum of an electron revolving in second order (n = 2) is

(a)

6.6 x 10-34 Js

(b)

3.3 x 10-34 Js

(c)

2.1 x 10-34 Js

(d)

9.27 x 10-34 Js

11. The magnetic declination for chennai is _______

(a)

-1° 5'

(b)

1°8'

(c)

-1°8'

(d)

1°5'

12. A wire of length 1 m carrying a current of 2 A is placed inside a field of magnetic induction 20 T such that it makes an angle of 30° with the direction of the field. The force experienced by the wire is

(a)

40N

(b)

10$\sqrt { 3 }$ N

(c)

20N

(d)

20$\sqrt { 3 }$N

13. To convert a galvanometer into an ammeter we connect which one of the following to the galvanometer?

(a)

a low resistance in series

(b)

a high resistance in series

(c)

a low resistance in parallel

(d)

a high resistance in parallel

14. The resistance of the filament of a 110 W, 220 V electric bulb is,

(a)

440 Ω

(b)

220 Ω

(c)

484 Ω

(d)

848 Ω

15. These are behaving like thermistor

(a)

insulators and conductors

(b)

semiconductors and conductors

(c)

insulators and semiconductors

(d)

conductors and alloys

16. Which of the following principle is used in a thermopile?

(a)

Thomson effect

(b)

Peltier effect

(c)

Seebeck effect

(d)

Joules effect

17. In a thermocouple, temperature of the cold junction is 20°C, the inversion of temperature is 600°C, then neutral temperature is

(a)

310°C

(b)

320°C

(c)

300°C

(d)

315°C

18. A deutron and an alpha particle move in a magnetic field along the same circular path, then the ratio of their velocities is _______

(a)

1:2

(b)

2:1

(c)

4:1

(d)

1:1

19. If a deutron and an alpha particle move perpendicular to a uniform magnetic field with same velocity, then the ratio of the radii of their path is ______

(a)

1:1

(b)

1:2

(c)

2:1

(d)

4:1

20. The period T of circular motion of a particle of mass m and charge q moving inside a uniform magnetic field of induction B is given by ______

(a)

Bq = Tm

(b)

T=$\frac { Bq }{ 2\pi m }$

(c)

BqT = 2πm

(d)

TBM=2πq

21. The current through a solenoid of length 0.5 m with 400 turns produces a magnetic field 10-3 tesla. The current is _______

(a)

2A

(b)

20

(c)

1A

(d)

0.5 mA

22. The force between two parallel wires carrying current is _______

(a)

F=$\frac { { \mu }_{ 0 } }{ 2\pi } \frac { { I }_{ 1 }{ I }_{ 2 }l }{ a }$

(b)

F=$\frac { { \mu }_{ 0 } }{ 2\pi } \frac { { I }_{ 1 }{ I }_{ 2 }l }{ al }$

(c)

F=$\frac { { \mu }_{ 0 } }{ 2\pi } \frac { { I }_{ 1 }{ I }_{ 2 } }{ a.l }$

(d)

F=$\frac { { \mu }_{ 0 } }{ 2\pi } { I }_{ 1 }{ I }_{ 2 }\frac { l }{ a }$

23. No current flows between two charged particles when connected if they have same ______

(a)

capcity

(b)

potential

(c)

charge

(d)

none of these

24. Torque acting on a coil is maximum when the coil is ______

(a)

parallel to the magnetic field

(b)

perpendicular to the magnetic field

(c)

at an angle of 45° to the magnetic field

(d)

at any position in a uniform magnetic field

25. If a current 0.5mA produces a deflection of 156°, then the galvanometer constant is about, ______

(a)

(b)

(c)