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What is a Resistor?

A resistor
is a component that decreases
the current in

a circuit. A resistor
transfers electrical energy into

heat energy.
See the theory of the resistance
of wires.

How is Resistance Calculated?

We can calculate resistance using the equation

voltage = current x resistance V = I x R.

Firstly, we need to measure the
current
flowing

through the resistor and the
voltage
across the resistor.

The
circuit diagram above shows

where to place an ammeter and a voltmeter.

The equation

voltage = current x resistance
V = I x R

can be rearranged to give

resistance
= voltage
÷ current
R =
V
÷ I

If the ammeter reads 2 A, and the voltmeter reads 6 V,

then R =
V
÷ I

= 6
÷ 2

=
3 ohms.

The same method can be used to

calculate the resistance of any component.

Links Electricity Resistance Revision Questions

gcsescience.com Physics Quiz Index Electricity Quiz gcsescience.com

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