Ncert Exercises & Solutions

The line that draws power supply to your house from the street has

(a)	zero average current
(b)	\(220\) V average voltage
(c)	voltage and current out of phase by \(90^\circ\)
(d)	voltage and current possibly differing in phase \(\phi\) such that \(\|\phi\|<\dfrac \pi 2\)

Choose the correct options:
1. (b), (c)
2. (a), (d)
3. (b), (d)
4. (a), (c)

(a, d) Hint: AC currents are used in domestic supplies.

For household supplies, AC currents are used which are having zero average value over a cycle.

The line is having some resistance so the power factor,

\cos ϕ = \frac{R}{Z} \neq 0

So, ϕ \neq π / 2 \Rightarrow ϕ < π / 2

i . e ., phase lies between 0 and π / 2 .