March 27, 2019
Electromagnet
- Electric current in a conductor produces a magnetic field around it.
- When a wire is wound into a coil, a electromagnet can be constructed. When electric current flows through the wire, the magnet is turned on. When electric current does not flow through the wire, the magnet is turned off.
Magnetic Field Patterns of Current Through Different Shapes of Wire
- Current through a straight line
- Current through a flat circular coil
- Current through a solenoid
Force on a Current-Carrying Wire in a Magnetic Field
When a current flows through a wire in a magnetic field,
- Magnetic field is produced by the electric current.
- This magnetic field interacts with the already existing magnetic field.
- The current-carrying wire in a magnetic field experiences force acting on it due to the interaction.
The magnitude of the force on the wire can be increased by
- increasing the magnitude of magnetic field
- increasing current flow in the wire
The direction of the force can be determined using Fleming's left hand rule:
When the thumb, index finger and middle finger of your left hand are held so that they are all perpendicular to each other,
- The thumb points in the direction of force.
- The index finger points in the direction of the original magnetic field.
- The middle finger points in the direction of the current.
Example 1
A metal rod XY is placed in a magnetic field. Wires from a cell are connected to the ends of the rod so that the current flows from X to Y. Describe the effect on the rod.
- The current in the rod will generate magnetic field around the rod.
- As the generated magnetic field interacts with the magnetic field that the rod is placed in, the rod will feel a force acting on it.
- The rod moves in the direction of the force.
- Using Fleming's left hand rule, we can determine that the direction of the force is pointing out of the screen.