JEE Mains · Physics · STD 12 -7. Alternating current
An \(AC\) source rated \(220\, V , 50\, Hz\) is connected to a resistor. The time taken by the current to change from its maximum to the rms value is
- A \(2.5\, ms\)
- B \(25\, ms\)
- C \(2.5\, s\)
- D \(0.25\, ms\)
Answer & Solution
Correct Answer
(A) \(2.5\, ms\)
Step-by-step Solution
Detailed explanation
\(i = i _{0} \cos (\omega t )\) \(i = i _{0}\) at \(t =0\) \(i =\frac{ i _{0}}{\sqrt{2}}\) at \(\omega t =\frac{\pi}{4}\) \(t =\frac{\pi}{4 \omega}=\frac{\pi}{4(2 \pi f )}=\frac{1}{8 f }\) \(t =\frac{1}{400}=2.5 ms\)
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