physics important mcqs Multiple Choice Questions of Electric Current and Ohm’s Law

1.Resistivity of a wire depends on :

(A) length

(B) material

(C) cross section area

(D) none of the above.

2. When n resistances each of value r are connected in parallel, then

resultant resistance is x. When these n

resistances are connected in series,

total resistance is:

(A) nx

(B) rnx

(C) x / n

(D) n2 x

3. Resistance of a wire is r ohms. The wire is stretched to double its length,

then its resistance in ohms is:

(A) r / 2

(B) 4 r

(C) 2 r

(D) r / 4.

4. Kirchhoff’s second law is based on law of conservation of:

(A) charge

(B) energy

(C) momentum

(D) mass.

5. The diameter of the nucleus of an atom is of the order of :

(A) 10 -31 m

(B) 10 -25 m

(C) 10 -21 m

(D) 10 -14m.

6. The mass of proton is roughly how many times the mass of an electron?

(A) 184,000

(B) 184,00

(C) 1840

(D)184.

7. The charge on an electron is known to be

1.6 x 10-19 coulomb. In a circuit

the current flowing is 1 A. How many

electrons will be flowing through the

circuit in a second?

(A) 1.6 x 1019

(B) 1.6 x 10-19

(C) 0.625 x 1019

(D) 0.625 x 1011

8. Two bulbs marked 200 watt-250 volts and 100 watt-250 volts are

joined in series to 250 volts supply.

Power consumed in circuit is:

(A) 33 watt

(B) 67 watt

(C) 100 watt

(D) 300 watt.

9. Ampere second could be the unit of:

(A) power

(B) conductance

(C) energy

(D) charge.

10. Which of the following is not the same as watt?

(A) joule/sec

(B) amperes/volt

(C) amperes x volts

(D) ( amperes )2 x ohm.

11. One kilowatt hour of electrical energy is the same as:

(A) 36 x 105 watts

(B) 36 x 10s ergs

(C) 36 x 105 joules

(D) 36 x 105 B.T.U.

12. An electric current of 5 A is same as:

(A) 5 J / C

(B) 5 V / C

(C) 5 C / sec

(D) 5 w / sec.

13. An electron of mass m kg and having a charge of e coulombs travels

from rest through a potential

difference of V volts. Its kinetic energy

will be: (A) eV Joules

(B) meV Joules

(C)me / V Joules

(D)V / me Joules.

14. The value of the following is given by 100 (kilo ampere ) x ( micro

ampere ) 100 milli ampere * 10

ampere:

(A) 0.001 A

(B) 0.1 A

(C) 1 A

(D) 10A.

15. A circuit contains two un-equal resistances in parallel:

(A) current is same in both

(B). large current flows in larger

resistor

(C). potential difference across each is

same

(D). smaller resistance has smaller

conductance.