- Explain an activity to show that a current-carrying conductor experiences a force when placed in a magnetic field.
- State the rule which gives the direction of force acting on the conductor.
- An electron moves perpendicular to a magnetic field as shown in the figure.
What would be the direction of force experienced on the electron?
A small aluminium rod suspended horizontally from a stand using two connecting wires. Place a strong horseshoe magnet in such a way that the rod lies between the two poles with the magnetic field directed upwards. For this, put the north pole of the magnet vertically below and south pole vertically above the aluminium rod. Connect the aluminium rod in series with a battery, a key and a rheostat. Pass a current through the aluminium rod from one end to other (B to A ). The rod is displaced towards left. When the direction of current flowing through the rod is reversed, the displacement of rod across towards right.
Fleming’s left-hand rule.
Stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular to one another. If the forefinger points in the direction of magnetic field and the middle finger in the direction of current, then the thumb will points in the direction of motion or the force acting on the conductor.
According to Fleming’s left hand rule, the direction of force is perpendicular to the direction of magnetic field and current. We know that the direction of current is taken opposite to the direction of motion of electrons. Therefore, the force is directed upwards from the plane of the paper.