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Magnetic Field

A magnetic field is the region around a magnet or a current-carrying conductor where magnetic force can be felt.

In one line: Magnetic field means magnet's reach, not the metal itself.

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Understand it

  • A magnetic field tells us where a magnet can attract or repel another magnetic object.
  • Around a bar magnet, the field is strongest near the poles.
  • Around a current-carrying wire, the field is produced by the electric current itself.
  • In exams, students should remember that the magnetic field is not a material object; it is the effect shown by force and field lines.

Example

If a compass needle is placed near a bar magnet, it turns because the needle experiences the magnet's field. Similarly, a current-carrying wire can deflect a compass near it.

Formula and rule

A magnetic field is represented by field lines; closer lines mean a stronger field, and the direction outside a magnet is from north pole to south pole.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

A student places a compass 2 cm from a straight wire carrying current.

  1. 1The needle deflects.
  2. 2This shows that the wire produces a magnetic field around itself, and the field is strong enough at that point to change the needle's direction.

Method you can reuse

  1. 1Identify the source of magnetism, such as a magnet or current-carrying wire.
  2. 2State that the region around it where force acts is the magnetic field.
  3. 3Mention how a compass or iron object responds.
  4. 4Link the response to the presence of field lines or magnetic influence.

Sketch it in your answer

Draw a bar magnet with curved field lines emerging from the north pole and entering the south pole. Show a compass needle tangent to the field line near the magnet.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why does a compass needle move when placed near a current-carrying wire?

Think first, then show answer
The wire produces a magnetic field around it, and that field exerts a turning effect on the compass needle. The needle moves because it aligns itself with the local magnetic field direction.

Common wrong answer

The field is only the magnet itself.

Why it loses marks: The field spreads around the magnet and can act at a distance.

Don't mix this up

Many students think the magnetic field exists only inside the magnet. In fact, it extends into the surrounding space.

Exam tip

When a question asks about magnetic influence, mention both the source and the region around it where force acts.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Explain what magnetic field means, or describe the observation when a compass is placed near a magnet or current-carrying conductor.
  1. 1

    Enough for 1 mark

    A magnetic field is the region around a magnet or a current-carrying conductor where magnetic force can be felt.

  2. 2

    Add for 2 marks

    Example: If a compass needle is placed near a bar magnet, it turns because the needle experiences the magnet's field. Similarly, a current-carrying wire can deflect a compass near it.

  3. 3

    Add for 3 marks

    A magnetic field tells us where a magnet can attract or repel another magnetic object.

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