Question

What is the r.m.s. value of an alternating current which when passed through a resistor produces heat which is thrice of that produced by a direct current of 2 amperes in the same resistor?

• A. 6 A
• B. 2 A
• C. 3.46 A
• D. 0.66 A

Answer 1

Answer: (C)

Heat produced by $AC =3 \times$ Heat produced by $DC$
$\therefore i_{ rms }^{2} R t=3 \times i^{2} R t$
$ \Rightarrow i_{ rms }^{2}=3 \times 2^{2}$
$\Rightarrow i_{ rms }=2 \sqrt{3}=3.46\, A$