Question

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?

Answer 1

Let us consider an AC series LCR circuit of angular frequency ω. The impedance of the circuit is given by,
`Z =sqrt(R^2 + (omegaL - 1/(omegaC))`
The phase difference between V and I is given by,
`tan Ø = (omegaL - 1/(omegaC))/Z`
From the above formula, we can clearly see that
`Ø ∈ = (-pi/2 , pi/2)`
So, we cannot have a phase difference of 180° or 120°.