CIE A Level Physics复习笔记20.1.11 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

Both wires will attract if their currents are in the same direction and repel if in opposite directions

• 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

• 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