Question

An alternating current of peak value 14 A is used to heat a metal wire. To produce the same heating effect, a constant current i can be used, where i is

(a) 14 A
(b) about 20 A
(c) 7 A
(d) about 10 A

Answer 1

(d) about 10 A

The rms value of an alternating current is equivalent to the constant current. So, the heating effect produced is actually measured in terms of the rms value, in case of alternating current. The constant current is, thus, equal to the rms value of alternating current, which is given by,
$I_{rms}=\frac{I_{peak}}{\sqrt{2}}=\frac{14}{\sqrt{2}}=9.9\approx 10\mathrm{A}$