Class 10 Science

Magnetic Effect of Electric Current: Magnetic field and Circular Loop

These notes are based on the chapter Magnetic Effect of Electric current class 10 science NCERT book and CBSE syllabus.

In the previous part of this chapter you have read about magnetic field due to current through a straight conductor. What happens to the direction of magnetic field when the conductor is twisted to form a loop?

In case of a circular current carrying conductor, the magnetic field is produced in the same manner as it happens in case of a straight current carrying conductor.


You can imagine hundreds of bangles strung over a rope or wire. Imagine that the rope or wire is circular loop and current if flowing through this loop. Now, imagine that the bangles are magnetic field lines.

In case of a circular current carrying conductor, the magnetic field lines would be in the form of concentric circles around every part of the periphery of the conductor. Since, magnetic field lines tend to remain closer when near the conductor, so the magnetic field would be stronger near the periphery of the loop.

On the other hand, the magnetic field lines would be distant from each other when we move towards the centre of the current carrying loop. Finally, at the centre, the arcs of big circles would appear as a straight lines.

maxwell's corckscrew rule

This figure shows a conductor in the shape of a circle or a loop.

You can imagine that a straight conductor has been twisted to make a loop. The way magnetic field lines make circles around a straight conductor, they make similar circles around the loop-like conductor.

You can see that circles are smaller near the conducting wire. As we move away from the conductor, i.e. towards the centre of the loop, the magnetic field lines take the form of straight lines. In fact, these lines are part of a bigger circle, and appear as straight lines because of very big diameter of the circle.

The direction of magnetic field can be identified using Right Hand Thumb's Rule. Let us assume that the current is moving in anti-clockwise direction in the loop. In that case, the magnetic field would be in clockwise direction, at the top of the loop. Moreover, it would be in anticlockwise direction at the bottom of the loop.

On the next page, you will read about solenoid.

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