A current carrying wire in a magnetic field

A current carrying wire in a magnetic field We know that a wire carrying a current can be made into an electromagnet. Consequently, such a wire will behave like a magnet. If this wire is placed near a permanent magnet, it will experience a force. We can use Flemings left hand rule to predict the direction of this force. In fact, we can also use it to predict the direction of any one of the following (if the direction of the other two is known). • the direction of flow of conventional current. • the direction of the magnetic field (from north to south). • the direction of the force exerted on the wire. © Boardworks Ltd 2003

Flemings Left Hand Rule Force (thumb) Field (first finger) Current (second finger) © Boardworks Ltd 2003

Animation of a current carrying wire in a magnetic field © Boardworks Ltd 2003

How could you increase the strength of the force? More current TRUE/FALSE More resistance TRUE/FALSE Stronger TRUE/FALSE magnetic field © Boardworks Ltd 2003

The DC Motor Uses Motor effect principle. How does it work? Each side of coil pushed in opposite direction due to motor effect. This results in the coil rotating. N S What happens if you reverse the direction of The coil spin in current orwill magnetic opposite direction. field? © Boardworks Ltd 2003

Electromagnetic induction What will happen if you move a magnet into a coil of wire? A current is induced in the coil. Only when the magnet is moving. © Boardworks Ltd 2003

Stationery magnet What happens when the magnet is in the coil? Nothing!! A current is only induced when the magnet is moving. © Boardworks Ltd 2003

Electromagnetic induction What will happen if you move the magnet out of the coil of wire? A current is induced in the coil. This time in the opposite direction. If you reverse the direction of the movement, then you reverse the direction of the current. © Boardworks Ltd 2003

AC or DC? What will happen if you move a magnet in and out of the coil repeatedly? A current will be induced in the coil, the current will flow in one direction and then reverse and flow in the opposite direction. What type of current is this? Alternating current © Boardworks Ltd 2003

Increasing the size of the current How can you increase the size of the current? more coils stronger magnetic field faster movement © Boardworks Ltd 2003

AC generator What are the four ways you can increase the current from an AC generator? 1. 2. 3. 4. Faster movement ___________ Stronger magnetic field ___________ More coils ___________ Larger area of coils ___________ ? © Boardworks Ltd 2003