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A flow of 10⁷ electrons per second in a conducting wire constitutes a current of

Asked in CBSE AIPMT 1994 · Current and charge flow

(1) 1.6×10⁻¹² A
(2) 1.6×10²⁶ A
(3) 1.6×10⁻²⁶ A
(4) 1.6×10¹² A

Answer: (1) 1.6×10⁻¹² A

Step-by-step solution

Idea: current is charge per second, I = ne where n is the number of electrons crossing per second.

I = 10⁷×1.6×10⁻¹⁹

I = 1.6×10⁻¹² A.

Why the other options are wrong

(2) Comes from writing the electronic charge as 1.6×10¹⁹ C, dropping the minus sign of its exponent.
(3) Comes from dividing e by the rate, 1.6×10⁻¹⁹/10⁷, instead of multiplying.
(4) Right mantissa with the sign of the exponent lost; 10¹² A is absurd for ten million electrons a second.

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