Past Year - 5 Mark Questions

Class 10
Chapter 13 Class 10 - Magnetic Effects of Electric Current

## 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 .

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