WAEC - Physics (1992 - No. 45)
Calculate the time in which 4.8 kJ of energy would be expended when an electric heater of resistance 1.8 x 103Ω is used on a 240 V mains supply. (Neglect heat losses to the surrounding).
150.0s
90.0s
36.0s
20.0s
2.7s.
Vysvětlení
E = V2t/R
t =
ERV2
= 4800 x 1.8 x 103240 x 240
= 150s