Resistance (Oxford AQA IGCSE Combined Science Double Award)

Resistance

• Electrical components resist the flow of charge that passes through them

  • This is called resistance

• Every electrical component has a resistance, even wires

  • In exam questions, the resistance of the wires, batteries, ammeters and voltmeters are assumed to be negligible

• Resistors can be used in circuits to control the amount of current present

• When the potential difference, V across a component remains constant then:

  • The greater its resistance R, then the smaller the current I that can pass through

  • The lower the resistance R then the larger the current I that can pass through

Relationship between current and resistance

• The resistance of a component can be found by measuring the current through and potential difference across, the component.

• The relationship between the potential difference, current and resistance is given by the equation for Ohm's law:

• Where:

  • V is the potential difference measured in volts, V

  • I is the current measured in amperes (often just called amps), A

  • R is the resistance measured in ohms (the Greek letter omega), Ω

Formula triangle for Ohm's law