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WORKSHEET 1 (CURRENT ELECTRICITY)(DRIFT VELOCITY ,

OHM’S LAW)

1) A steady current flows in a metallic conductor of non-uniform cross-section. The
quantity/quantities constant along the length of the conductor is/are:

(a)current, electric field and drift speed

(b)drift speed only

(c)current and drift speed

(d)current only

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2) The current in a conductor varies with time t as I=2t + 3t , where I is in ampere and t in
second. Electric charge flowing through a section of the conductor during t=2 s to t= 3 s is:

(a)10 C (b)24 C (c)33 C (d)44 C

3) Masses of three wires of copper are in the ratio 1:3:5 and their lengths are in the ratio 5:3:1.
The ratio of their electrical resistances are:

(a)1:3:5 (b)5:3:1 (c)1:15:125 (d)125:15:1

4) Current density is a …………………………. quantity.

5) S.I unit of mobility is…………………………………..

6) The alloys which are used for making resistances have low temperature coefficient of
resistance and high…………………………………………….

7) The electron drift speed is estimated to be a few mm/s for currents in the range of a few

amperes. How then is current established the instant a circuit is closed?

8) Two conducting wires X and Y of diameter in the ratio 2:1 but different materials are joined
in series across a battery. If number density of electrons in X is twice that in Y, find the ratio of
drift velocity of electrons in the two wires.

9) Establish a relation between drift velocity and time of relaxation.

10) Derive an expression for drift velocity of electrons in a conductor. Hence deduce Ohm’s law.