Aresistor dissipates 0.25 w when current of 20 ma passes through it. part a how much current would be needed for the resistor to dissipate 0.50 w? how much current would be needed for the resistor to dissipate 0.50 ? 56 ma 28 ma 40 ma 80 ma

Power dissipated by a resistor = (current)² x (resistance).

0.25 W = (0.02 A)² x (resistance)

This resistor = (0.25 W) / (0.02 A)²

This resistor = 625 ohms

If we want it to dissipate 0.5 W, then

0.5 W = (current)² x (625 ohms)

Current = √(0.5/625)

Current = √(0.0008)

Current = 28.28 mA

A slightly easier way:

Since the power is = I²R, it grows in proportion to (current)² .

We want to double the power dissipated, so we only need to increase the current by the factor of √2 .

(20 mA) x (√2) = 28.28 mA

hypothesising or postulating