Question

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

• A. $14A$
• B. about $20A$
• C. $7A$
• D. about $10A$

Answer 1

Answer: (D)

about $10A$

The rms value an AC current is equal to the dc current that delivers the same average power to a resistor as the periodic current. Therefore, the constant current i that produces the same heating effect as AC current of peak value 14A, in a metal wire is :

$I_{rms}=\frac{I_{peak}}{\sqrt{2}}=\frac{14}{\sqrt{2}}=9.899A$