A 10   Ω resistance is connected across 220   V - 50   Hz AC supply. The time taken by…

A 10 Ω resistance is connected across 220 V-50 Hz AC supply. The time taken by the current to change from its maximum value to the rms value is:
  1. 2.5 ms
  2. 1.5 ms
  3. 3.0 ms
  4. 4.5 ms

Solution

⇒i=i0sinωt

When i=i0

i0=i0sinωt1⇒ωt1=π2 …(1)

When i=i02

i02=i0sinωt2⇒ωt2=π4 …(2)

Time taken by current from maximum value to rms value, ⇒t1-t2=π2ω-π4ω=π4ω=π4×2πf

=18×50

=1400sec

=2.5 ms

Asked in: JEE Main 2021 (25 Jul Shift 2)

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