 # Class 12th Physics Chapter 3 Current Electricity Imoprtant Objective Question

Current Electricity

1. Which one of the following is the best material for making connecting wires?

(A) Nichrome

(B) Tungsten

(C) Copper

(D) Manganese

2. Fuse-wire is made of which material ?

(A) Copper

(B) Tungsten

(P) Nichrome

3. Three resistors of resistance Reach are combined in various ways. Which of the following cannot be obtained ?

(A) 3R

(B) 2R/4

(C) R/3

(D) 2R/3

4. A 220 V, 1000 W Bulb is connected to a 110V supply. The power consumed by bulb will be :

(A) 750 W

(B) 500 W

(C) 250 W

(D) 1000 W

5. If on increasing the temperature, resistance decreases then it is :

(A) Superconductor

(B) Semiconductor

(C) Insulator

(D) None of these

6. The wire of an electric heater (100W,200V) is cut from middle into two equal parts. These parts are connected together in parallel and then connected to the same 200V source. The power liberated is now :

(A) 40 W

(B) 50 W

(C) 25 W

(D) 200 W

7. You are given three resistances each of one ohm. The maximum resistance that can be obtained by their combination is

(A) 1 ohm

(B) 1 / 2 ohm

(C) 2 ohm

(D) 3 Ω

8. In the figure, the equivalent resistance between ‘a’ and ‘b’ is

(A) 1 Ω

(B) 3 Ω

(C) 6 Ω

(D) None of these

9. The resistance of an ideal voltmeter is

(A) infinite

(B) zero

(C) 50000 Ω

(D)None of these

10. The resistance of an ideal ammeter is

(A) zero

(B) very small

(C) very large

(D) infinite

11. The resistance of a resistor is R. It is in series with a variable resistance. Initially both the resistance are equal. The total initial resistance is

(A) R

(B) 2R

(C) R / 2

(D) zero

12. The equivalent resistance between points A and B of the given circuit is,

(A) R

(B) R / 2

(C) 2R

(D) None of these

13. The SI unit of temperature co-efficient of resistivity is

(A) Ω mK-1

(B) K-1

(C) Ω-1

(D) Sm-1

14. If the temperature is increased by 3°C, the value of temperature co-efficient of resistivity.

(A) increases

(B) decreases

(C) remains almost the same

(D) None of these

15. The temperature of electric bulb just after it is switched on

(A) goes on increasing

(B) first decreases then decreases

(C) first decreases then increases

(D) first increases and then becomes constant

16. The heat generated by a 100W heater in 2 minutes is equal to which of the following?

(A) 4 x 103

(B) 6 x 103 J

(C) 10 x 103J

(D) 12 x 103J

17. A heater is rated as 1000W, 230V. Its resistance is

(A) 22.9 Ω

(B) 32.9 Ω

(C) 42.9 Ω

(D) 52.9 Ω

18. The resistance of a metal, when heated, goes on

(A) decreasing this

(B) increasing

(C) remaining the same

(D) becoming zero

19. The Kirchhoff’s point rule obeys the principle of conservation of

(A) energy

(B) charge

(C) momentum

(D) mass

20. The property of a circuit that converts electrical energy into thermal energy is called,

(A) resistance

(B) current

(C) voltage

(D) electromotive force

21. The cause of flow of current in a conductor is different in

(A) resistance

(B) temperature

(C) electric potential

(D) None of these

22. When a cell of emf 2V is connected in circuit, a maximum of 5A current is obtained. Its internal resistance in ohm is

(A) 0.4

(B) 10

(C) 2.5

(D) 7

23. If the resistance in a circuit at constant potential difference is halved, the heat generated will became

(A) half

(B) double

(C) four times

(D) unchanged

24. The electrical appliances in our houses are connected across supply switch in

(A) series

(B) parallel

(C) mixed grouping

(D) None of these

25. Negative charges flow from

(A) low to high potential

(B) high to low potential

(C) independent of potential where

(D) None of these

26. The current passing through a thermocouple is called

(A) Seebeck current

(B) Joule current

(C) Peltier current

(D) None of these

27. Wheatstone bridge is used to measure

(A) electromotive force

(B) current

(C) resistance

(D) charge

28. Thermo-couple is a device that converts

(A) electrical energy into thermal energy

(B) mechanical energy into thermal energy

(C) thermal energy into electrical energy

(D) None of these

29. The specific resistance of conductor increase with:

(A) increase of temperature

(B) increase of cross-sectional area

(C) decrease of the cross-sectional area

(D) decrease in length