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: