If you are reading this you are using electricity. It
turns out that electricity and magnetism are two symptoms of a single
underlying thing. There is a force which acts between protons and electrons,
which we call electromagnetism. This force is attractive been a proton and an
electron, but repulsive between electrons or between protons. When we talk
about an electric current flowing in a circuit, we actually mean that electrons
are being forced to move around the circuit by an electromagnetic force.
Crudely you can think of a battery as a container in which protons and
electrons start evenly spread out. When you charge the battery, the charger
applies an electromagnetic force that makes the electrons pile-up in one part
of the battery, leaving too few electrons in the other part. When you then use
the battery, all the electrons that have been piled up rush back (via your
phone, or torch, or car starter motor, or whatever) to the other part of the
battery. When there’s no longer any build-up of electrons the battery is flat.
If you want a nice analogy to understand batteries, try
this. Imagine a tank half filled with water. The water level is the same
throughout the tank. Now imagine you put a divider in the middle of the tank so
water can’t flow from one side to the other. Then imagine using a bucket or
pump to lift water from one side to the other over the divider. You’ll end up
with the tank nearly full on one side and nearly empty on the other. The water
on the full side would like to drop down into the empty half of the tank but it
can’t because the divider is in the way. Now suppose you connect the two halves
of the tank at the bottom with a pipe. The water from the full half of the tank
will rush through the pipe to the empty half. Gradually the level on one side
of the tank will fall, and the level on the other side will rise until the
level is the same throughout, then the water will stop flowing in the pipe. In
this analogy the water tank is the battery and the pipe is the electric
circuit.
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