do now! can you stick the sheet in your book please?
TRANSCRIPT
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Do now!
Can you stick the sheet in your book please?
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Last lesson
• Field around a wire
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Moving charges (currents)
Moving charges (electric currents) also produce a magnetic field
http://www.sciencebuddies.org
Conventional current – electrons flow in the opposite direction
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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
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To make an electromagnet stronger?
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To make an electromagnet strongerThe 3 C’s
• More Coils
• More Current
• Use an iron Core
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Today’s lesson
• Field patterns around a wire, solenoid and coil.
• The motor effect
• Making a loudspeaker
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Shape around a single coil of wire
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Field around a coil
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A side view
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Field around a solenoid (coil)
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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.
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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
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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!
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Sample question
In this example, which way will the wire be pushed? (red is north on the magnets)
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Sample question
In this example, which way will the wire be pushed? (red is north on the magnets)
Current
Field
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Building a loudspeaker
These also use the motor effect
Coil in here
magnet