# Force on current-carrying conductor

Show/Hide Sub-topics (Magnetism & Electromagnetism | O Level)

When current-carrying conductor is placed in a magnetic field, it will experience a force when the magnetic field direction is not parallel to the current direction. The magnitude of the force is maximum when the magnetic field and current directions are mutually perpendicular to each other. The force decreases when the angle between the magnetic field and current directions is smaller than $90^{\circ}$.

Factors that affect the strength of the force:

• Angle between the magnetic field and current directions (More about this below)
• Magnetic field strength (Stronger magnetic field $\rightarrow$ stronger force)
• Amount of current in conductor (Higher current $\rightarrow$ stronger force)
• Length of conductor within magnetic field (Longer conductor $\rightarrow$ stronger force)

If the current direction is PARALLEL to the magnetic field, there will NO force on the conductor by the magnetic field. The magnitude of the force is MAXIMUM when the angle between the magnetic field and current direction is $90^{\circ}$.

This is commonly exploited to produce a turning effect in a current-carrying coil to produce an electric motor.

It does not have to be a current carrying conductor to experience a force due to the magnetic field. The magnetic field actually interacts with the moving electrons in the conductor to produce the force. Hence, electrons that are moving in the direction perpendicular to the magnetic field will experience the force as well. This means that if you pass an electron beam through a magnetic field, it will be deflected. (provided it is perpendicular)