Force on a Current Carrying Conductor in a Magnetic Field

1. Aim: To demonstrate the force experienced by a current-carrying conductor in a magnetic field and observe how the direction of force changes with current and magnetic field direction.

2. Requirements: flexible copper wire, a stand to hold the wire, an electric cell (battery) to supply current, a horseshoe magnet with a strong magnetic field, a switch and connecting wires.

3. Procedure

• Set up the apparatus as shown in the diagram, fixing the copper wire so that it passes through the poles of the horseshoe magnet.
• Ensure the wire is straight when no current flows (Position A).
• Turn on the switch to allow current to flow from top to bottom. Observe that the wire bends into Position C.
• Reverse the current direction (bottom to top) and note that the wire bends into Position B.
• Reverse the magnet’s poles (swap North and South) and observe how the force direction changes again.

Force acting on a current-carrying conductor in the presence of a magnetic field

4. Observations

• The conductor moves when current flows, proving that a force is exerted on it.
• The force is perpendicular to both the current direction and the magnetic field.
• Reversing the current reverses the direction of force.
• Reversing the magnet’s poles also reverses the force’s direction.

5. Conclusion: A current-carrying conductor placed in a magnetic field experiences a force (Lorentz Force).

The force direction follows Fleming’s Left-Hand Rule: If the thumb, forefinger, and middle finger of the left hand are perpendicular, with the forefinger pointing in the magnetic field direction and the middle finger in the current direction, the thumb indicates the force direction. The force is strongest when the current is perpendicular to the magnetic field.