A current of 1 mA is flowing through a copper wire. How many electrons will pass a given point in one second  $\left[\mathrm{e}<mspace\; width="1em"></mspace>=<mspace\; width="1em"></mspace>1.6<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^{-19}<mspace\; width="1em"></mspace>\mathrm{Coulomb}\right]$

1.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^{19}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

2.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^{15}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

3.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^{31}<mspace\; width="1em"></mspace><mspace\; width="1em"></mspace>$

4.  $6.25<mspace\; width="1em"></mspace>\times <mspace\; width="1em"></mspace>{10}^8$

The drift velocity of free electrons in a conductor is \(v\) when a current \(i\) is flowing in it. If both the radius and current are doubled, then the drift velocity will be:

Drift velocity \(v_d\) varies with the intensity of the electric field as per the relation:
1. \(v_{d} \propto E\)
2. \(v_{d} \propto \frac{1}{E}\)
3. \(v_{d}= \text{constant}\)
4. \(v_{d} \propto E^2\)

In a conductor 4 coulombs of charge flows for 2 seconds. The value of electric current will be :

1. 4 volts

2. 4 amperes

3. 2 amperes

4. 2 volts

Through a semiconductor, an electric current is due to drift off:

1. Free electrons

2. Free electrons and holes

3. Positive and negative ions

4. Protons