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#### Current Electricity Book Back Questions

12th Standard EM

Reg.No. :
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Physics

Time : 00:45:00 Hrs
Total Marks : 30
5 x 1 = 5
1. A toaster operating at 240 V has a resistance of 120 Ω. Th e power is

(a)

400 W

(b)

2 W

(c)

480 W

(d)

240 W

2. What is the value of resistance of the following resistor?

(a)

100 k Ω

(b)

10 k Ω

(c)

1k Ω

(d)

1000 k Ω

3. In India electricity is supplied for domestic use at 220 V. It is supplied at 110 V in USA. If the resistance of a 60W bulb for use in India is R, the resistance of a 60W bulb for use in USA will be

(a)

R

(b)

2R

(c)

$\frac{R}{4}$

(d)

$\frac{R}{2}$

4. The temperature coefficient of resistance of a wire is 0.00125 per °C. At 300 K, its resistance is 1 Ω. The resistance of the wire will be 2 Ω at

(a)

1154 K

(b)

1100 K

(c)

1400 K

(d)

1127 K

5. A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of

(a)

each of them increases

(b)

each of them decreases

(c)

copper increases and germanium decreases

(d)

copper decreases and germanium increases

6. 3 x 2 = 6
7. Distinguish between drift velocity and mobility.

8. What is Seebeck effect?

9. What is Peltier effect?

10. 3 x 3 = 9
11. Compute the current in the wire if a charge of 120 C is flowing through a copper wire in 1 minute.

12. Calculate the equivalent resistance for the circuit which is connected to 24 V battery and also find the potential difference across 4 Ω and 6 Ω resistors in the circuit.

13. When two resistances connected in series and parallel their equivalent resistances are 15 Ω and $\frac{56}{15}$Ω respectively. Find the individual resistances.

14. 2 x 5 = 10
15. Two electric bulbs marked 20 W – 220 V and 100 W – 220 V are connected in series to 440 V supply. Which bulb will be fused?

16. From the given circuit find the value of I.