Solution

ID: past-exam-of-the-physics-2-paper-of-the-university-of-oxford/2016/11/i/b/solution

A parallel connection has the same electric potential difference across each element, so the electrical admittances add. With and ,
For a prescribed sinusoidal current, . Thus the voltage-minus-current phase is
Below the circuit is inductive, so electric potential difference leads current; above it the circuit is capacitive, so electric potential difference lags current. At , the reactive branch currents cancel, and . This is the impedance maximum for positive finite , whereas the series circuit has its impedance minimum at the same frequency. It does not mean that either individual reactive branch current vanishes.

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