Question

The voltage across a component is measured as 80 V r.m.s. and the current through it is 4 A r.m.s. If the current leads the voltage by 20° what is the apparent power in the component?

Answer 1

The apparent power in the component can be calculated using the formula:

Apparent power (S) = voltage (V) x current (I)

However, since the current is leading the voltage by 20°, we need to use the complex power formula:

S = VI*

where V* represents the complex conjugate of the voltage.

To find V*, we need to change the phase angle of the voltage by 180° since it is lagging the current. Therefore:

V* = 80 ∠-20° = 80 ∠160°

Now we can calculate the complex power:

S = VI* = 80 ∠20° x 4 ∠-20° = 320 ∠0°

The apparent power in the component is 320 VA.

Answer 2

The apparent power in the component is 301.52 VA.