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