Question

A purely resistive device is rated as $12\text{A}$ and $120\text{V}$ for DC supply. If it is connected with an AC supply, $V=250\sin \left(30t\right)$, find the expression of current$\left(i\right)$ flowing in the circuit.

• A. $i=25\cos \left(30t\right)$
• B. $i=25\sin \left(30t\right)$
• C. $i=50\cos \left(15t\right)$
• D. $i=50\sin \left(15t\right)$

Answer 1

The correct option is B $i=25\sin \left(30t\right)$

The resistance of the device is,

$R=\frac{V}{I}=\frac{120}{12}=10\Omega$

Current flowing in this device when connected to the AC supply is,

$i=\frac{V}{R}=\frac{250\sin \left(30t\right)}{10}=25\sin \left(30t\right)$

Hence, option $\left(B\right)$ is the correct answer.