A 2.0 kW heater element from a dryer has a length of 80 cm. If a 10 cm section is removed, what power is used by the now shortened element at 120 V?

A 120-V immersion heater consists of a coil of wire that is placed in a cup to boil the water. The heater can boil one cup of 20.00 °C water in 180.00 seconds. You buy one to use in your dorm room, but you are worried that you will overload the circuit and trip the 15.00-A, 120-V circuit breaker, which supplies your dorm room. In your dorm room, you have four 100.00-W incandescent lamps and a 1500.00-W space heater. (a) What is the power rating of the immersion heater? (b) Will it trip the breaker when everything is turned on? (c) If it you replace the incandescent bulbs with 18.00-W LED, will the breaker trip when everything is turned on?

a) A freezer that is never turned off draws an average current of 2.4 A when it is plugged into a 115 V outlet.  What is the yearly cost of operating the freezer if the average cost of electricity is $0.14/kWh [round your final answer to zero decimal places]?  b) If you were to replace the freezer in the question above with one that draws an average current of 3.5 A, it would result in a lower electricity cost. True or False?

If one wants to design a 1500 W electrical heater that consists of a resistor R with V = 208 V across it, what value should be chosen for R?

#20

How much could you pay to replace a 60 W incandescent light bulb with a 15 W compact fluorescent bulb if electricity in your area costs 10 cents per kilowatt hour and you paid 25 cents for the incandescent bulb? You estimate that you will break even after about 1000 hours.

If electrical energy costs $0.12 per kilowatt-hour, how much do the following events cost? (a) To burn a 120-W lightbulb for 24 h. $ (b) To operate an electric oven for 6.6 h if it carries a current of 20.0 A at 220 V. $