the power consumed in a circuit element will be least when the phase difference between the current and voltage is

The power consumed in a circuit element is least when the phase difference between the current and voltage is 90° (i.e., ϕ=90∘\phi =90^\circ ϕ=90∘).

Quick explanation

In an AC circuit, average power is

P=VrmsIrmscos⁡ϕP=V_{\text{rms}}I_{\text{rms}}\cos\phi P=Vrms​Irms​cosϕ

where ϕ\phi ϕ is the phase difference between voltage and current.

• When ϕ=0∘\phi =0^\circ ϕ=0∘, cos⁡ϕ=1\cos\phi =1cosϕ=1: power is maximum.

• When ϕ=90∘\phi =90^\circ ϕ=90∘, cos⁡ϕ=0\cos\phi =0cosϕ=0: average power becomes zero, which is the least possible value.

So, from the usual options (0°, 60°, 90°, 180°), the correct choice is 90°.

Final answer for your question: 90°.