An immersion heater rated 1000W, 220V is used to heat 0.01m3 of water.

1.	An immersion heater rated 1000W, 220V is used to heat 0.01m3 of water. Assuming that the power is supplied at 220V and 60% of the power supplied is used to heat the water, how long will it take to increase the temperature of the water from 15°C to 40° C?
Answer» P = 1000 V = 220v R = V²/P = 48400/1000 = 48.4Ω Mass of water = 1/100 x 1000 = 10kg Heat required to raise the temp. of given amount of water = msΔt = 10 × 4200 × 25 = 1050000 Now heat liberated is only 60%. So V²/R x T x 60% = 1050000 => (220)²/48.4 x 60/100 x T = 1050000 => T = 10500/6 x 1/60nub = 29.16min

An immersion heater rated 1000W, 220V is used to heat 0.01m3 of water. Assuming that the power is supplied at 220V and 60% of the power supplied is used to heat the water, how long will it take to increase the temperature of the water from 15°C to 40° C?

Answer»

P = 1000

V = 220v

R = V²/P = 48400/1000 = 48.4Ω

Mass of water = 1/100 x 1000 = 10kg

Heat required to raise the temp. of given amount of water = msΔt = 10 × 4200 × 25 = 1050000

Now heat liberated is only 60%. So V²/R x T x 60% = 1050000

=> (220)²/48.4 x 60/100 x T = 1050000 => T = 10500/6 x 1/60nub = 29.16min