Question

You are going camping and want a way to heat up water for coffee in the morning without making a fire. You have electric water, which is really just a resistor, that can heat 360 grams of water (approximately 12 oz or the size of a tall coffee from Starbucks) from 20C to 90C in 3.00 minutes when attached to the 120 V wall outlet. Assuming that 90% of the energy drawn from the power source goes into the heating the water, how long will it take you to heat the water for your 12 oz coffee if instead you use your 12.0-v car battery as a power supply?

Answer 1