#### Current Electricity Model Question Paper

12th Standard EM

Reg.No. :
•
•
•
•
•
•

Physics

Time : 01:30:00 Hrs
Total Marks : 50
6 x 1 = 6
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. Two wires of A and B with circular cross section made up of the same material with equal lengths. Suppose RA = 3 RB, then what is the ratio of radius of wire A to that of B?

(a)

3

(b)

$\sqrt3$

(c)

$\frac{1}{\sqrt3}$

(d)

$\frac{1}{3}$

3. 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

4. In Joule’s heating law, when I and t are constant, if the H is taken along the y axis and I2 along the x axis, the graph is

(a)

straight line

(b)

parabola

(c)

circle

(d)

ellipse

5. The temperature co-efficient of resistance for alloys is

(a)

low

(b)

very low

(c)

high

(d)

very high

6. If the specific resistance of a potentiometer wire is 10-7 Om and current flowing through it . is 0.1 amp, cross - sectional area of wire is 10-6 m2, then potential gradient will be

(a)

10-2 v/m

(b)

10-4 v/m

(c)

10-6 v/m

(d)

10-8v/m

7. 5 x 1 = 5
8. Electric Heaters

9. (1)

Nichrome

10. Electric furnace

11. (2)

Tungsten

12. Electrical Lamp

13. (3)

joule

14. Current

15. (4)

Molybdenum

16. Energy

17. (5)

ampere

10 x 2 = 20
18. Why current is a scalar?

19. Distinguish between drift velocity and mobility.

20. State macroscopic form of Ohm’s law.

21. Define current density.

22. State Kirchhoff’s voltage rule.

23. What is Seebeck effect?

24. What is Peltier effect?

25. Define current.

26. Define resistance

27. What is thermoelectric effect?

28. 3 x 3 = 9
29. Determine the number of electrons flowing per second through a conductor, when a current of 32 A flows through it.

30. The resistance of a wire is 20 Ω. What will be new resistance, if it is stretched uniformly 8 times its original length?

31. Obtain the macroscopic form of Ohm’s law from its microscopic form and discuss its limitation.

32. 2 x 5 = 10
33. 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?

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