**Points :**Current Electricity, mcqs, Current Electricity fill in the blanks, mechanics objective type questions 1. The specific resistance of all metals is most affected by

(a) applied magnetic field

(b) illumination

(c) pressure

(d)

**temperature**

2. Through a metallic conductor an electric current is passed due to the drift of

(a)

**protons**

(b) neutrons

(c) +ve ions

(d) free electrons

3. Through an electrolyte an electric current is passed due to the drift of

(a) protons

(b) free electrons

(c) + ye and -ye ions

(d)

**free electrons and holes**

4. There is a current of 3.2 amp in a conductor. The number of electrons that cross any section normal to the direction of flow per second is

(a) 2 x 10

^{19}

(b) 0.2 x 10

^{19}

(c)

**20 x 10**

^{19}(d) 200 x 10

^{19}

5. Which of the following has a positive temperature coefficient of resistance?

(a) germanium

(b) an electrolye

(c) carbon

(d)

**copper**

6. The fact that the conductance of some metals rises to infinity at some temperature below a few degrees kelvin is called

(a) optical conductivity

(b) thermal conductivity

(c)

**magnetic conductivity**

(d) superconductivity

7. To deposit one litre of hydrogen at 22.4 atm from acidulated water, the quantity of electricity that must pass through is

(a) 22.4 coulomb

(b) 1 coulomb

(c) 193000 coulomb

(d)

**96500 coulomb**

8. Kirchoffâ€™s 1st law is based on the law of conservation of

(a) energy

(b) momentum

(c) mass

(d)

**charge**

9. The equivalent resistance of resistors in parallel is always

(a) equal to the sum of the component resistors

(b) higher than the highest of component resistors

(c) less than the lowest of component resistors

(d)

**in between the lowest and the highest of component resistors**

10. A cell of negligible resistance and emf 2 volt is connected to a series combination of 2, 3 and 5 ohms. The potential difference in volts between the terminals of 3 ohm resistance will be

(a) 0.4 V

(b) 0.5V

(c) 0.6V

(d)

**0.7V**

11. If a metallic block has no potential difference applied across it, then the mean velocity of free electron is

(a)

**inversely proportional to T**

(b) directly proportional to T

(c) directly proportional to IT

(d) zero

12. The equivalent resistance of resistors in series is always

(a) equal to the sum of the component resistors

(b) in between the lowest and the highest of component resistors

(c)

**equal to the mean of the component resistors**

(d) less than the lowest of the component resistors

13. The example of a non-ohmic resistance is

(a) tungsten wire

(b)

**carbon resistance**

(c) copper wire

(d) diode

14. Three resistances of magnitude 2,3 and 5 ohms are connected in parallel to a battery of 10 volts and of negligible resistance. The potential drop across the 3 ohm resistance will be

(a)

**0 volts**

(b) 10 volts

(c) 20 volts

(d) 30 volts

15. The specific resistance of a wire

(a) varies with its mass

(b) varies with its length

(c) varies with its area of cross-section

(d)

**is independent of length, mass, area of cross-section**

16. The resistance of a 20 cm long wire is 5 ohms. The wire is stretched to a uniform wire of 40 cm length. The resistance now will be

(a) 2 ohm

(b) 20 ohm

(c) 200 ohm

(d)

**2000 ohm**

17. When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance becomes.

(a) thirteen times

(b)

**fourteen times**

(c) fifteen times

(d) sixteen times

18. A primary cell has emf. 2 volt. When short circuited it gives a current of 4 amp. Its internal resistance in ohms will be

(a) 0.3

(b) 0.4

(c)

**0.5**

(d) 0.6

19. Two resistances are joined in parallel whose resultant is 6/5 ohm. One of the resistance wire is broken and the effective resistance becomes 2 ohms. Then the resistance in ohms of the wire that got broken was

(a) 1

(b) 2

(c)

**3**

(d) 4

20. Four wires of equal length and of resistance 10 ohms each are connected in the form of a square. The equivalent resistance between two opposite corners of the square is

(a) 0 ohms

(b) 10 ohms

(c)

**20 ohms**

(d) 30 ohms

21. Water can be made conducting by adding a small amount of any of the following except

(a) Cu SO

_{4}

(b)

**Na Cl**

(c) NH

_{4}Cl

(d) Sugar

22. To deposit one gm equivalent of an element at an electrode, one needs a charge equal to

(a) one statcoulomb

(b) one absolute coulomb

(c) one coulomb

(d)

**96500 coulomb**

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