Q12 of 51 Page 328

Can you have an AC series circuit in which there is a phase difference of (a) 180° (b) 120° between the emf and the current?

(a) No. (b) No.

For an LCR circuit with angular frequency ω, the impedance is given by the formula


where R = resistance, L = inductance, C = capacitance.


Now, the phase difference between the current and the voltage is given by the formula , where = phase difference, ω = angular frequency, L = inductance, C = capacitance, R = resistance.


Since there are no restrictions on the values of L, C or R, it is obvious that can take any value between -∞ to +∞, that is can take any value between -900 to +900 (since tan 900 = ∞)


Since both 1200 and 1800 fall beyond the permitted range of values, we cannot have an AC circuit with any of the given phase differences. (Ans)


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