Multiple Choice
An AC emf source is given by . What is the instantaneous emf of this source at?
31. Alternating Current
Alternating Voltages and Currents
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The current in an AC circuit takes 0.02 s to change direction. What is the angular frequency of the AC source?
A
6.4×10−3 s−1
B
0.04 s−1
C
0.25 s−1
D
157 s−1
Verified step by step guidance1
Understand that the time given, 0.02 s, is the time taken for the current to change direction, which corresponds to half of the period of the AC cycle.
The full period (T) of the AC cycle is twice the time taken for the current to change direction, so T = 2 * 0.02 s = 0.04 s.
Recall the relationship between angular frequency (ω) and period (T): ω = 2π / T.
Substitute the value of the period into the formula: ω = 2π / 0.04 s.
Calculate the angular frequency using the formula, which will give you the correct answer of 157 s⁻¹.
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