Albert Teen

YOU ARE LEARNING:

The Right Hand Thumb Rule

The Right Hand Thumb Rule

The Right Hand Thumb Rule

We can use the Right Hand Thumb Rule to find the direction of the magnetic field produced by a current-carrying wire.

When a current flows through a wire it creates a magnetic field around the wire. Which of the following methods could we use to determine the direction of the magnetic field?

1

We can use the magnetic needle in a compass to detect the magnetic field around a wire carrying a current.

The compass gives us the direction because the needle will always point to a specific pole. Iron filings for example, can't tell us which way is which.

What do you think will happen to the direction of the magnetic field if we change the direction of the current that is flowing through the wire?

Why do you think a change in direction of the current causes a change in direction of the magnetic fields?

You can imagine a current carrying wire having a general north and south pole. Remember that a magnetic field always points from north to south. So if we reverse the current, the magnetic field will change direction because essentially we are reversing the north and south poles.

1

We can use our right hand to show the direction of the magnetic field created by a carrying wire.

Using your right hand, point your thumb in the direction of the current and curl your fingers. Your finger tips will curl around in the direction of the circular magnetic field.

2

Imagine a vertical wire, where the current is running from the top of the wire to the bottom. What will the direction of the magnetic field around the wire be?

A) Clockwise B) Anticlockwise

What effect will increasing the current through the wire have on the strength of the magnetic field around the wire?

It is the current flowing through the wire that causes the magnetic field, so the more current you have, the stronger the magnetic field will be.

What effect does increasing the distance from the wire have on the strength of a magnetic field?