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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.

Electrical Circuit used to Calculate Resistance

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
esistance = 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.

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