# Do now! Can you stick the sheet in your book please?

## Presentation on theme: "Do now! Can you stick the sheet in your book please?"— Presentation transcript:

Last lesson Field around a wire

Moving charges (currents) Moving charges (electric currents) also produce a magnetic field http://www.sciencebuddies.org Conventional current – electrons flow in the opposite direction

Magnetic field around a straight wire Stronger field closer to wire You can use the right hand screw rule to decide which direction the field goes

To make an electromagnet stronger?

To make an electromagnet stronger The 3 C’s More Coils More Current Use an iron Core

Today’s lesson Field patterns around a wire, solenoid and coil. The motor effect Making a loudspeaker

Shape around a single coil of wire

Field around a coil

A side view

Field around a solenoid (coil)

The Motor Effect When a current is placed in a magnetic field it will experience a force (provided the current is not parallel to the field). This is called the motor effect. Can you copy this sentence into your books please.

The Motor Effect The direction of the force on a current in a magnetic field is given by Flemming’s left hand rule. Centre finger = Conventional Current First finger = Field direction Thumb = Motion

The Motor Effect The direction of the force on a current in a magnetic field is given by Flemming’s left hand rule. Centre finger = Conventional Current (+ to -) First finger = Field direction (N to S) Thumb = Motion Can you copy this please? WITH DIAGRAM!

Sample question In this example, which way will the wire be pushed? (red is north on the magnets)

Sample question In this example, which way will the wire be pushed? (red is north on the magnets) Current Field

Building a loudspeaker These also use the motor effect Coil in here magnet