1a) The heater uses 1800 W (watts) of power.
1b) The cost to operate the heater for 30 days is 1800 W x 5.0 h x 30 days x $.10/kWh = $540.
2a) The amount of coal burned during a year for a family of four is 48,000 kWh x 1.0 kg/33.0 mJ x 40% efficiency = 57600 kg.
2b) The pile of coal would be 57600 kg/2620 kg/m^3 = 22 m^3.
2c) The amount of heat given off to the environment is 48,000 kWh x 1.0 kg/33.0 mJ = 14400 MJ.
3a) The cost of operating the light bulb for 30 days is 65 W x 6 h x 30 days x $.10/kWh = $117.
3b) The cost of operating the digital clock for 30 days is 5 W x 24 h x 30 days x $.10/kWh = $72.
1. An electric space heater draws 15.0 A from a 120 V source. It is operated, on average, for 5.0h (hours) each day. a) How much power does the heater use and b) At $.10 per kWh, what does it cost to operate the heater for 30 days?
2. Suppose each person in the United States uses 12,000 kWh of electricity a year and the power plants using coal to generate electricity are 40% efficient. If 1.0 kg of burned coal releases 33.0 mJ a) how much coal will be burned during a year for a family of four b) how large a pile of coal would that be (using 2620 kg/ m^3) c) how much heat is given off to the environment
3. A light bulb uses 65 watts (used for 6 hours a day) and a digital clock uses 5 watts (used for 24hrs a day). Find the cost of operating each one for 30 days. Assume the price is $.10 per kWh
The equations given=
power= current x voltage, energy= power x time, cost= energy x price
I can find a) at 1800 w (watts), but I have no idea where to start on part b.
For 2, I'm unsure of where to star. I know the family of four would use 48,000 kWh a year, but after that, I'm lost. Could you please help explain it to me?
1 answer
1 answer