What are magnetic field lines? List three characteristics of these lines. Describe in brief an activity to study the magnetic field lines due to a current flowing in a circular coil.
Magnetic field lines are imaginary lines along which the north magnetic pole would move in a magnetic field.The tangent at any point on the magnetic field line gives the direction of the magnetic field at that point.
Characteristics of magnetic field lines are:
- Field lines arise from the North pole and end into the South pole of the magnet.
- Field lines are closed curves.
- Field lines are closer in stronger magnetic fields.
- Field lines never intersect each other as for two lines to intersect, there must be two directions of magnetic field at a point, which is not possible.
- Direction of field lines inside a magnet is from South to North.
- The relative strength of the magnetic field is shown by the degree of closeness of field lines.
Activity to study the magnetic field lines due to a current flowing in a circular coil:
- A rectangular cardboard having holes is taken and a circular coil is passed through the holes . The coil is kept normal to the cardboard.
- The ends of the coil are connected to a battery through a key.
- Iron filings are sprinkled uniformly on the cardboard . Key is plugged in.
- On tapping cardboard gently the iron filings get arranged in concentric circular loops around the holes on the cardboard indicating the magnetic field lines .