# 25.4.2 Forces Between Current-Carrying Conductors

### Origin of the Forces Between Current-Carrying Conductors

• A current carrying conductor, such as a wire, produces a magnetic field around it
• The direction of the field depends on the direction of the current through the wire
• This is determined by the right hand thumb rule
• Parallel current-carrying conductors will therefore either attract or repel each other
• If the currents are in the same direction in both conductors, the magnetic field lines between the conductors cancel out – the conductors will attract each other
• If the currents are in the opposite direction in both conductors, the magnetic field lines between the conductors push each other apart – the conductors will repel each other
• When the conductors attract, the direction of the magnetic forces will be towards each other
• When the conductors repel, the direction of the magnetic forces will be away from each other
• The magnitude of each force depend on the amount of current and length of the wire

#### Worked example

• Newton’s Third Law states:
• When two bodies interact, the force on one body is equal but opposite in direction to the force on the other body
• Therefore, the forces on the wires act in equal but opposite directions

### Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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