What’s a Watt? Activity
The electricity we use in our homes and schools is measured in units called
watts. Because power plants generate so much electricity, the electricity they
make is measured in much larger units called megawatts. What’s a
megawatt? It’s one million watts. What’s a watt? Well, that’s a little more
difficult to explain.
To understand watts you must first understand amps and volts. Amps are a
measure of the amount of electricity used. Volts measure the pressure, or
force, of electricity. The amps multiplied by the volts gives you the watts, a
measure of the work that electricity does per second.


Use the formula amps x volts = watts to figure out how many watts these typical appliances use. (Most homes are served by 120volt electricity, so we will use that as the value for volts in
our equation.)
Appliance 
Amps 
x 
Volts = 
Watts 
Hair dryer on high 
12 
x 
120 = 
____________ 
Space heater 
10 
x 
120 = 
____________ 
Vacuum cleaner 
8 
x 
120 = 
____________ 
Ceiling lamp 
1 
x 
120 = 
____________ 
Answering machine 
.5 
x 
120 = 
____________ 
It may help you understand watts to think of electricity
like water flowing through a hose. The amount of water
that can fit through the hose depends on the diameter of
the hose (amps). The force of the water depends on how
far open the faucet is (volts). The work that can be done
(watts) depends on both the amount and the pressure of
the water (amps x volts = watts).


