JAMB - Physics (2002 - No. 32)
An electric iron is rated 1000W, 230V. What is the resistance of its elements?
51.9Ω
52.9Ω
55.9Ω
57.6Ω
Giải thích
Electric Power = IV = I2R = V2/R thus for a device rated 1000 W, 230V, from the relation P = V2/R, 1000 = (230)2/R
=> R = (230)2/1000
= 52900/1000 = 52.9Ω
=> R = (230)2/1000
= 52900/1000 = 52.9Ω