Electric Resistance (SL IB Physics)

• As electrons move through a conductor within a circuit (or any other component), they transfer some of their electrical potential energy to the positive ions of the metal

Free electrons collide with metal ions which resist their flow

• This transfer of energy results in an increase in the kinetic energy of the atoms in the lattice
  • This raises the overall internal energy of the metal

• The macroscopic result of this transfer is the heating up of the wire which causes resistance
• Some metals heat up more than others
  • The greater the heating effect, the higher the resistance
  • Copper has a low electrical resistance, making it an ideal material to make wires from

• All electrical components have resistance to different degrees, including the wires and batteries
• Voltmeters and ammeters are said to be ideal when
  • An ideal voltmeter has infinite resistance, such that no current passes through it
  • An ideal ammeter has zero resistance, such that all the current passes through it

• The resistance R of a component is defined as:

The ratio of the potential difference across the component to the current flowing through it 

• It is calculated as follows:

• Where:
  • V = potential difference (V)
  • I = electric current (A)
  • R = resistance (Ω)

• The units for resistance is ohms represented by the greek letter 'omega', Ω

• The higher the resistance of a component, the lower the current flowing through it and vice versa
• In terms of SI base units: 1 Ω = 1 kg m² s^–3 A^–2