Question

An emf E = 4cos (1000t volt) is applied to an L–R circuit of inductance 3 mH and resistance 4 $\Omega$ . The amplitude of the current in the circuit is:

• A. $1.0A$
• B. $0.8A$
• C. $\frac{A}{\sqrt{7}}A$
• D. $\frac{5}{7}A$

Answer 1

The correct option is B $0.8A$

$I_0=\frac{V_0}{\sqrt{R^2+(Lw{)}^2}}=\frac{4}{\sqrt{4^2+[3\times {10}^{-3}\times {10}^3{]}^2}}$
$=\frac{4}{\sqrt{4^2+3^2}}=\frac{4}{5}$
= 0.8 A