Question

A resistance of 20 ohm is connected to a source of an alternating potential V = 220 sin (100pt). The time taken by the current to change from its peak value to rms value is-

• A. 0.2 sec
• B. 0.25 sec
• C. 25 × 10^–3sec
• D. 2.5 × 10^–3sec

Answer 1

Answer: (D)

2.5 × 10^–3sec

Answer 2

$\frac{V_{0}}{\sqrt{2}}$ = V₀ sin(wt)

$\frac{2\pi}{T}$ × t = $\frac{\pi}{4}$ Ž t₁ = $\frac{7}{8}$

Time taken to reach the peak is $\frac{T}{4}$

\ interval = $\frac{T}{4} - \frac{T}{8}$ = $\frac{T}{8}$ = $\frac{1}{8f} = \frac{1}{8 \times 50}$

= $\frac{1}{400}$ = 2.5 × 10^–3 sec.