Elenco Electronic Playground 50-in-1 Experiments - Manual (Page 7)

The Resistor: Why is the water pipe that goes to your
kitchen faucet smaller than the one that comes to your
house from the water company? And why is it much
smaller than the main water line that supplies water to
your entire town? Because you don’t need so much
water. The pipe size limits the water flow to what you
actually need. Electricity works in a similar manner,
except that wires have so little resistance that they would
have to be very, very thin to limit the flow of electricity.
They would be hard to handle and break easily. But the
water flow through a large pipe could also be limited by
filling a section of the pipe with rocks (a thin screen would
keep the rocks from falling over), which would slow the flow of water but not stop it. Resistors are like rocks for
electricity, they control how much electric current flows.
The resistance, expressed in ohms (
Ω, named after
George Ohm), kilohms (K
Ω, 1000 ohms), or megohms
(M
Ω, 1,000,000 ohms) is a measure of how much a
resistor resists the flow of electricity. To increase the
water flow through a pipe you can increase the water
pressure or use less rocks. To increase the electric
current in a circuit you can increase the voltage or use a
lower value resistor (this will be demonstrated in a
moment). The symbol for the resistor is shown on the
right.
Rocks in Pipe Resistor Resistor Symbol
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