Power Supplies
All electronic circuits need a supply of electricity to work.
There are four sources:-
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| Wet Batteries |
Dry Batteries |
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| Power Supply Unit | Alternative Sources |
Dry Cells (torch batteries) are the most commonly used source of electricty. Wet cells (car batteries) produce much higher power.
Now that the price of Solar Cell are coming down, they being used more.
Clockwork is starting to reappear to produce electricity.
Wind-up radio and mobile phone emergency power pack are good examples.
There are many economical mains Power Supply Units (PSU) on the market. This avoids making circuits with Mains Electricty with all the danger that involves.
Water is often used as an example to show how current flows around a circuit.
Many books use a picture of a water pump in a circuit. The pump produces a pressure which drives
the water around the pipe. They then go on to say that a battery is like the pump,
forcing the electricty around the circuit. Its called the Electro Motive Force and it is measured in Volts.
There is something wrong with this comparison. If you cut the pipe, the pump carries on pumping
and the water falls on the floor. If you break the electrical circuit, the battery actually stops producing the pressure E.M.F. Volts do not fall out of the end of the battery.
Batteries
How does a battery work.
When chemicals inside the battery react together, they produce excess electrons at one terminal and a shortage at the other. When the two terminals are connected together by a wire, electricity will flow through the wire. Electricity will only flow if the circuit is complete.
Primary Cells.
Dry batteries are small and use a paste electrolyte. They can be both rechargeable and non-rechargeable.
