Quick Lab
Modeling a Fuse
Materials
6-volt battery, two wires with stripped ends, aluminum foil, scissors, wooden block, unpainted metal thumbtacks
Procedure
Connect the two wires to the two battery terminals.
Cut a strip of aluminum foil about 0.5 cm by 3 cm. In the center, cut the width down to 1 mm. Attach the ends of the foil strip to the wooden block with the thumbtacks.
Touch one of the wires to each end of the foil strip to form a circuit.
Observe what happens to the foil strip. CAUTION If the wire and the battery become very hot, remove the wires from the foil.
Analyze and Conclude
Observing What happened to the foil strip when the wires were attached to it?
Using Models How is the foil like a fuse? Explain.
An appliance's power rating lets you know how much power it uses under normal conditions. An electric stove uses about 6000 watts, and a microwave oven uses about 1000 watts. To find the electrical energy used by an appliance, multiply power by time.
Electrical Energy
For example, the power rating of a typical clothes dryer is 5400 watts, or 5.4 kilowatts. If you use the clothes dryer for 2 hours, the energy use is 5.4 kilowatts multiplied by 2 hours, or 10.8 kilowatt-hours. Electric power companies usually determine charges on your electric bill using kilowatt-hours as a unit of energy. A kilowatt-hour equals 3,600,000 joules.
Electrical Safety
Inspectors check all new houses to make sure electrical wiring is installed safely. All wires must be able to carry the maximum expected current. But correct wiring is not enough to prevent electrical accidents. 
Correct wiring, fuses, circuit breakers, insulation, and grounded plugs help make electrical energy safe to use.
In the United States, most household circuits usually have an average voltage of 120 volts. The amount of current in a circuit can vary, depending on the number of devices that are in the circuit. Each device that is turned on increases the current. If the current exceeds the circuit's safety limit, the wire may overheat and start a fire.
Home Safety
A fuse prevents current overload in a circuit. A wire in the center of the fuse melts if too much current passes through it. This melting is known as “blowing a fuse.” After a fuse like one of those shown in Figure 14 blows, it must be replaced with a new fuse before the circuit can carry a current again.
Most houses today use circuit breakers instead of fuses to prevent overloads. A circuit breaker is a switch that opens when current in a circuit is too high. The circuit breaker must be reset before the circuit can be used again.
Figure 14 Fuses have an internal wire that burns out if a current is too great.
Personal Safety
Imagine what could happen if your body became part of an electric circuit. Figure 15 shows some effects that current may have on a person. You might not notice a current of 1 milliamp, but higher currents can be quite dangerous.
Electrical wiring in a home is insulated to protect people. If the insulation is damaged, you may accidentally touch the bare wire and get a shock. Avoid touching electrical devices with wet hands because your hands conduct current more readily when they are wet.
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