Question

A current of 2.0 A existsin a wire of cross sectional area 1.0 mm square. If each cubic metre of the wire contains 6.0*10to power 28 free electron find drift speed

Answer 1

A current of 2A exists in a wire of cross sectional area 1 mm². each cubic metre of the wire contains 6 × 10^28 free electrons.

To find : The drift speed of electrons in the wire.

Solution : current passing through wire, i = 2A

cross sectional area , a = 1mm² = 10¯⁶ m²

number of electrons per m³ , n = 6 × 10^28

now using formula of drift speed,

v = i/nea

where e is charge on electron i.e., 1.6 × 10^-19 C

now v = (2 A)/(6 × 10^28 /m³ × 1.6 × 10^-19 C × 10¯⁶ m²)

= 2/(9.6 × 10³)

= 0.2083 × 10¯³ m/s

= 2.083 × 10¯⁴ m/s

Therefore the drift speed of electrons in the wire is 2.083 × 10¯⁴ m/s.