A resistance of 40 Ω is connected to a source of alternating current rated 220 V, 50 Hz. Find the time taken by the current to change from its maximum value to rms value :
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Question

A resistance of 40 Ω is connected to a source of alternating current rated 220 V, 50 Hz. Find the time taken by the current to change from its maximum value to rms value :

G1 Physics · Accepted Answer

For i=Iₘcosωt, Iᵣₘₛ=Iₘ/√2. From maximum current to rms current, phase changes by π/4. Therefore Δt=(π/4)/(2πf)=1/(8f)=2.5 ms. Hence option A.