JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Current Electricity

A current of 2 A flows through a wire of cross-sectional area

25.0 mm^{2}

. The number of free electrons in a cubic meter are

2.0 \times 1 0^{28}

. The drift velocity of the electrons is

____

\times 1 0^{- 6} ms^{- 1}

(given, charge on electron

= 1.6 \times 1 0^{- 19} C

)

Answer: 25

Solution

The drift velocity is related to current by:

v_{d} = \frac{I}{n e A}

where

n

is the number density of free electrons,

e

is the electron charge, and

A

is the cross-sectional area.

v_{d} = \frac{2}{2 \times 1 0 ^{28} \times 1.6 \times 1 0 ^{- 19} \times 25 \times 1 0 ^{- 6}} = 25 \times 1 0^{- 6} m/s

JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Integer answer