Question

There is a current of 1.344 amp in a copper wire
whose area of cross-section normal to the length of
the wire is 1mm2. If the number of free electrons per
cmis 8.4 x 1022, then the drift velocity would be-
(1) 1.0 mm per sec (2) 1.0 metre per sec
(3) 0.1 mm per sec (4) 0.01 mm per sec​

Answer 1

Given that,

Current, I = 1.344

Area of cross-section of the wire, $A=1\ mm^2=0.01\ m^2$

The number of free electrons per cm³ is $8.4\times 10^{22}$

To find,

The drift velocity.

Solution,

The formula used to find the drift velocity is given by :

$v_d=\dfrac{I}{nAe}$

e is charge of one elecron

$v_d=\dfrac{1.344}{8.4\times 10^{22}\times 0.01\times 1.6\times 10^{-19}}\\\\v_d=0.01\ cm/s$

or

$v_d=0.1\ mm/s$

So, the drift velocity would be 0.1 mm per sec.