Alat pemanas listrik tertulis 300 W, 200 V. Alat dipasang pada tegangan 100 V, maka daya yg terpakai adalah...Watt

P1 = 300 W
V1 = 200 V
V2 = 100 V
P2 = ... ?

Penyelesaian:
R1 : R2 = V²/P : V²/P
R1 : R2 = (200)²/(300) : (100)²/P
R1 : R2 = 40.000/300 : 10.000/P
40.000P = 3.000.000
4P = 300
P = 75 watt

P1 = 300 W
V1 = 200 V
V2 = 100 V

P2 = (V2/V1)² × P1
P2 = (100/200)² × 300
P2 = 0,25 × 300
P2 = 75 W