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Force between parallel wires
Intermediate
Parallel currents attract.
F/L = μ₀I₁I₂/2πdParallel currents attract and antiparallel currents repel with F/L = μ₀I₁I₂/(2πd).
Two 10 A wires 1 cm apart: 2 mN/m.
Opposite of electrostatic like charges.
In more detail
Two parallel wires carrying current attract if the currents are in the same direction and repel if they are opposite. The force per unit length is μ0I1I2/(2πd).
Real-world uses
- The definition of the ampere uses the force between parallel wires.
- Power cables experience forces during short circuits.
- Engineers designing power cables consider the magnetic forces between parallel wires, which can push or pull them together.
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Frequently asked questions
Why do they attract?
Each wire produces a field at the other, and the force between them pulls them together for parallel currents.
Does distance matter?
Yes, the force falls off as 1/d.
Do parallel currents attract or repel?
Currents in the same direction attract, while currents in opposite directions repel.
Related topics in Magnetism & Induction
Mass spectrometer · Cyclotron · Force on a current-carrying wire · Definition of the ampere · Torque on a current loop · Moving coil galvanometer