Question

A resistor and an inductor of negligible resistance are connected in series to a 20 V ac source. If the voltage across the resistor is 12 V, the voltage across the inductor will be ______.

Options

• 6 V

• 8 V

• 10 V

• 16 V

Answer 1

A resistor and an inductor of negligible resistance are connected in series to a 20 V ac source. If the voltage across the resistor is 12 V, the voltage across the inductor will be 16 V.

Explanation:

Given: V = 20 V

V_R = 12 V

Total voltage is the vector sum (phasor addition):

V² = `V_R^2 + V_L^2`

20² = `12^2 + V_L^2`

400 = `144 + V_L^2`

`V_L^2` = 400 − 144

`V_L^2` = 256

V_L = `sqrt 256`

V_L = 16 V