Current in a Torch Circuit

The battery gets its power to the lamp through the wires. This
is because the battery in a closed circuit creates “current” in
the wires which flows around the circuit. When current flows

through the lamp it lights up.

Current is measured in Amperes (Amps) - smaller currents in
electronic circuits are usually measured in milliamps (mA). A
milliamp is equal to one thousandth of an Amp.

1mA = 1/1000 Amp

Close the switch
to see the current flow from the positive (+) side of the battery to the negative (-) side.

If you had no lamp and just connected the battery ends
together with wire you would allow a very high current to flow.

Click on the switch to see what would happen to the wire if there was no lamp and a much larger car battery was being used.

 

Resistance

In the second circuit by connecting the two ends of the
battery together with wire, the battery has been “short-
circuited”. Because of this, there is very little or no
resistance
to the current that flows from the battery. The
wires connected to the car battery are glowing redhot and
soon melt.

 

In a circuit

Ohm's Law

says:

Voltage

= Current

x Resistance

(volts)

(amps)

(ohms)