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In an AC circuit the voltage and current are v = 5*sin(100*pi*t - pi/6) and i = 4*sin(100*pi*t + pi/6). Which statement about the phase relationship is correct?
- Voltage leads the current by 30 deg
- Current leads the voltage by 30 deg
- Current leads the voltage by 60 deg
- Voltage leads the current by 60 deg
Correct answer: Current leads the voltage by 60 deg
Solution
Phase of current = +pi/6 = +30 deg; phase of voltage = -pi/6 = -30 deg. The current's phase is ahead of the voltage's by (+30) - (-30) = 60 deg. Hence the current leads the voltage by 60 deg.
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