Electromagnetism part 2: electric motors and electromagnetic induction

TRIPLE: How would the magnetic field look like here? Remember to include the direction of the field

How can the strength of the magnetic field around a current-carrying wire be increased?

• Increasing the current in the wire

• Wrapping the wire into a coil or solenoid

What is a solenoid?

A long coil

Draw the magnetic field lines around this solenoid. Remember to indicate the direction of the magnetic field

The shape of the magnetic field around a solenoid is the same as that around a bar magnet

How can you determine the polarity of the solenoid? What happens if you reverse the direction of the current?

If you reverse direction of current, then the North and South poles will also switch

How can we increase the strength of the field around a solenoid?

• Increasing the current in the solenoid

• Increasing the number of turns on the solenoid

• Wrapping the solenoid around a magnetically soft core such as iron

  • This is often called an electromagnet

When does a charged particle experience a force in a wire?

When the charged particle is moving and crossing magnetic field lines it will experience a force

• A stationary particle experience NO force

• A particle moving parallel to the field experiences NO force