electric power and electrical energy use
electrical energy use
Did you ever wonder how much electrical energy it takes to use an appliance such as a hair dryer? Electrical energy use depends on the power of the appliance and how long it is used. It can be calculated with this equation: Electrical Energy = Power Time If Miranda uses her 1.8-kilowatt hair dryer for 0.2 hours, how much electrical energy does she use? Electrical Energy = 1.8 kilowatts 0.2 hours = 0.36 kilowatt-hours Electrical energy use is typically expressed in kilowatt-hours, as in this example. How much energy is this? One kilowatt-hour equals 3.6 million joules of energy. Q: Suppose Miranda were to use a 1.2-kilowatt hair dryer for 0.2 hours. How much electrical energy would she use then? A: She would use: Electrical Energy = 1.2 kilowatts 0.2 hour = 0.24 kilowatt-hours
The rate at which a device changes electric current to another form of energy is called electric power. The SI unit for powerincluding electric poweris the watt. A watt equals 1 joule of energy per second. High wattages are often expressed in kilowatts, where 1 kilowatt equals 1000 watts. The power of an electric device, such as a hair dryer, can be calculated if you know the voltage of the circuit and how much current the device receives. The following equation is used: Power (watts) = Current (amps) Voltage (volts) Assume that Mirandas hair dryer is the only electric device in a 120-volt circuit that carries 15 amps of current. Then the power of her hair dryer in kilowatts is: Power = 15 amps 120 volts = 1800 watts, or 1.8 kilowatts Q: If a different hair dryer is plugged into a 120-volt circuit that carries 10 amps of current. What is the power of the other hair dryer? A: Substitute these values in the power equation: Power = 10 amps 120 volts = 1200 watts, or 1.2 kilowatts
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electric power is the rate at which an electric device changes electrical energy to another form of energy.
--> a. true b. false
which equation can be used to calculate the power of an electric device?
--> a) power = current x voltage b) power = current/voltage c) power = voltage/current d) none of the above
a watt equals one
a) volt per second. b) amp per second. c) ohm per second. --> d) joule per second.
one kilowatt equals 100 watts.
a. true --> b. false
if an electric device in a 120-volt circuit uses 10 amps of current, then the power of the device is
--> a) 1200 watts. b) 130 watts. c) 110 watts. d) 12 watts.
which equation can be used to calculate the electrical energy used by an appliance?
a) energy = power/time --> b) energy = power x time c) energy = time/power d) energy = power + time
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