Question

The e.m.f E = 4 cos 1000t volts is applied to an L–R circuit containing inductance 3mH and resistance 4 W . The amplitude of current is –

• A. $4\sqrt{7}$A
• B. 1.0 A
• C. $\frac{4}{7}$A
• D. 0.8 A

Answer 1

Answer: (D)

0.8 A

Answer 2

i₀ = $\frac{v_{0}}{Z}$ ,

Z = $\sqrt{R^{2} + (\omega L)^{2}}$

= $\sqrt{4^{2} + (1000 \times 3 \times 10^{–3})^{2}}$ = 5 W

i₀ = $\frac{4}{5}$

i₀ = 0.8A