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Current Electricity

Question

At room temperature, copper has free electron density of 8.4 x 10²⁸ m^-3, The electron drift velocity in a copper conductor of cross-section area of 10^-6 m² and carrying a current of 5.4 A will be

4 ms^-1

0.4 ms^-1

4 ms^-1

0.4 mm s^-1

Solution

0.4 mm s^-1

Drift velocity in copper conductor

$v_{d} = \frac{i}{ne A}$

$v_{d} = \frac{5.4}{8.4 \times 10^{28} \times 1.6 \times 10^{- 19} \times 10^{- 6}}$

= 0.4 × 10^-3 ms^-1

$v_{d} = 0.4 mm s^{- 1}$