Concepts

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

If we are given direction of current,

How do we find Direction of Magnetic Field?

We find  Direction of Magnetic Field using Maxwell's Right-hand Thumb Rule

Suppose we hold an electric wire with our right hand as show below

Assuming current flows in direction of thumb (from bottom to top)

Direction of Magnetic field will be in Direction in which our finger curl (from from Left to Right Direction)

Hence,

when current flows from bottom to top, magnetic field is anticlockwise

There's another method which we can use - Maxwell's Corkscrew Rule

## Maxwell Corkscrew rule

What is a Corkscrew?

A corkscrew is a device which is used to pull cork from bottle

It contains a spiral metal rod and a handle

To find magnetic field using corkscrew rule -

When we turn a corkscrew clockwise (from right to left), it goes inside the cork

So, if magnetic field is clockwise, direction of current is inside

## Comparing Right hand Thumb Rule and Corkscrew Rule

 Right Hand thumb rule Corkscrew rule Suppose we are holding a straight current carrying wire in our right hand. Point the thumb in the direction in which the current is flowing The direction in which our fingers curl is the direction of the magnetic field. Suppose we have a corkscrew. Point the pointed tip of the corkscrew in the direction in which the current is flowing. The direction in which the screw rotates (clockwise) is the direction of the magnetic field.

### Summary

 Flow of Current Magnetic Field Direction Bottom to Top Clockwise (Left to Right) Top to Bottom Anticlockwise (Right to Left)

## Questions

NCERT Question 6 (c) - State whether the following statements are true or false.

The field at the centre of a long circular coil carrying current will be parallel straight lines.

NCERT Question 15 (i) - State the rule to determine the direction of a

(i) magnetic field produced around a straight conductor-carrying current,

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#### Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo