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Four time-varying currents in cases I, II, III and IV have rms values I1, I2, I3 and I4 respectively. Based on the standard waveforms (I and II equal peak symmetric, III the largest, IV the smallest), identify the correct relation among them.

1. I3 > I1 = I2 > I4
2. I1 = I2 = I3 = I4
3. I3 > I4 > I2 = I1
4. I3 > I2 > I1 > I4

Correct answer: I3 > I1 = I2 > I4

Solution

The rms current is the square root of the time-averaged square of the instantaneous current. For these standard waveforms, cases I and II yield identical rms values, case III (largest sustained magnitude) gives the highest, and case IV (smallest) gives the lowest, producing I3 > I1 = I2 > I4.

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