Peak, rms and half-cycle mean values kept apart, the phase and reactance table for pure R, L and C, LRC impedance with power factor, resonance and Q-factor, and the full-wave diode bridge.
Unit 4 carries 9 of the 50 physics marks, the largest single block in the paper; with seven chapters sharing them, this one averages a little over one (MEC publishes weights by unit, not by chapter). It is the chapter where a candidate either has the phase table in memory or does not. Everything in it — impedance, power factor, resonance, the choke coil — is built out of three lines: a resistor keeps current and voltage in step, an inductor makes the current lag by a quarter cycle, a capacitor makes it lead by a quarter cycle. Learn those three and the rest is Pythagoras.
The MEC scope lines are: Peak and rms values; Impedance, power, Q-factor and phase in LRC circuits; Rectification using a diode bridge. The three headings below are those points, in MEC's order. The emfs being fed in come from Electromagnetic induction.
Three ways it is asked:
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