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#### Electromagnetic Induction and Alternating Current One Mark Questions

12th Standard EM

Reg.No. :
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Physics

Time : 00:30:00 Hrs
Total Marks : 15
10 x 1 = 10
1. Th e fl ux linked with a coil at any instant t is given by $\Phi$B =10t2−50t+ 250 . The induced emf at t = 3s is

(a)

−190 V

(b)

−10 V

(c)

10 V

(d)

190 V

2. When the current changes from +2A to −2A in 0.05 s, an emf of 8 V is induced in a coil. Th e co-efficient of self-induction of the coil is

(a)

0.2H

(b)

0.4H

(c)

0.8H

(d)

0.1H

3. A step-down transformer reduces the supply voltage from 220 V to 11 V and increase the current from 6 A to 100 A. Then its efficiency is

(a)

1.2

(b)

0.83

(c)

0.12

(d)

0.9

4. In a series RL circuit, the resistance and inductive reactance are the same. Then the phase difference between the voltage and current in the circuit is

(a)

$\frac{\pi}{4}$

(b)

$\frac{\pi}{2}$

(c)

$\frac{\pi}{6}$

(d)

zero

5. An inductor 20 mH, a capacitor 50 μF and a resistor 40 Ω are connected in series across a source of emf v = 10 sin 340 t. The power loss in AC circuit is

(a)

0.76 W

(b)

0.89 W

(c)

0.46 W

(d)

0.67 W

6. The unit henry can also be written as

(a)

VS A-1

(b)

Wb A-1

(c)

Ωs

(d)

all

7. The self-inductance of a straight conductor is

(a)

zero

(b)

infinity

(c)

very large

(d)

very small

8. An emf of 12V is induced when the current in the coil changes at the rate of 40 A S-1. The coefficient of self induction of the coil is

(a)

0.3 H

(b)

0.003 H

(c)

30 H

(d)

4.8 H

9. An emf of 12V is induced when the current in the coil changes at the rate of 40 A S-1. The coefficient of self induction of the coil is

(a)

0.3 H

(b)

0.003 H

(c)

30 H

(d)

4.8 H

10. Transformer works on

(a)

AC only

(b)

DC only

(c)

both AC and DC

(d)

AC more effectively than DC

11. 5 x 1 = 5

13. (1)

14. Ac circuit with resistor

15. (2)

Electromagnetic Induction

16. Ac circuit with inductor

17. (3)

Predominantly Inductive

18. Ac circult with capacitor

19. (4)

20. RLC circuit

21. (5)

Voltage and current are in phase