Make Electronics

Experiencing Electricity 11

Experiment 2: Let’s Abuse a Battery!

First inspect the fuse very carefully, using a magnifying glass if you have one.
You should see a tiny S-shape in the transparent window at the center of the
fuse. That S is a thin section of metal that melts easily.

Remove the battery that you short-circuited. It is no longer useful for anything,
and should be recycled if possible. Put a fresh battery into the battery carrier,
connect the fuse as shown in Figure 1-35, and take another look. You should
see a break in the center of the S shape, where the metal melted almost in-
stantly. Figure 1-36 shows the fuse before you connected it, and Figure 1-37
depicts a blown fuse. This is how a fuse works: it melts to protect the rest of
the circuit. That tiny break inside the fuse stops any more current from flowing.

FundAmentAls

Volt    basics  

Electrical pressure is measured in volts. The volt is an international unit. A millivolt

is 1/1,000 of a volt.

Number of volts Usually expressed as Abbreviated as

0.001 volts 1 millivolt 1 mV

0.01 volts 10 millivolts 10 mV

0.1 volts 100 millivolts 100 mV

1 volt 1,000 millivolts 1V

Ampere  basics  

We measure electrical flow in amperes, or amps. The ampere is an international

unit, often referred to as an “amp.” A milliamp is 1/1,000 of an ampere.

Number of amperes Usually expressed as Abbreviated as

0.001 amps 1 milliamp 1 mA

0.01 amps 10 milliamps 10 mA

0.1 amps 100 milliamps 100 mA

1 amp 1,000 milliamps 1A

Figure 1-35. When you attach both wires to

the fuse, the little S-shaped element inside

will melt almost instantly.

Figure 1-36. A 3-amp fuse, before its

element was melted by a single 1.5-volt

battery.

Figure 1-37. The same fuse after being

melted by electric current.