7.1 Flashcards
Describe the forces produced when magnets are brought together.
- Force of repulsion when two like poles brought together.
- Force fo attraction when two opposite poles brought together.
What is the difference between permanent and induced magnets?
- Permanent magnet produces its own magnetic field.
- Induced magnets only become magnets when placed in a magnetic field (always is force of attraction).
What are the four types of magnetic materials?
- Iron
- Steel
- Copper
- Cobalt
What is a magnetic field?
Region around magnet where a force acts on another magnet or on a magnetic material.
Describe how to plot the magnetic field of magnet.
- Place compass at North Pole of bar magnet.
- Draw cross at North Pole of compass.
- Place South of compass on cross and plot North with a cross.
- Repeat this step until a complete magnetic field line is plotted.
- Connect crosses and draw direction of field line using arrow.
- Repeat steps 1-5 starting at different point of bar magnet’s North pole.
Describe the evidence that the Earth’s core is magnetic.
If a compass is held away from any magnet, the needle always points to the North - South direction - Earth has magnetic field due to core.
Describe how to prove a current flowing through a wire generates a magnetic field.
- Place compass near circuit.
- When the current is turned off, the compass needle aligns with the Earth’s magnetic field.
- When the current is turned on, the compass needle deflects proving there is a magnetic field around the wire.
Explain how a solenoid can increase the magnetic effect of a current.
- Increase size of current
- Increase number of turn of solenoid.
- Place iron core into solenoid (electromagnet)
[Describe how to] Draw the magnetic field pattern for a straight wire carrying a current.
Individual circles around the wire all in the same direction.
[Describe how to] Draw the magnetic field pattern for a solenoid carrying a current.
Similar to magnetic field of bar magnet.
- From centre of solenoid, it goes out and wraps around the solenoid.
- The middle field line is straight.
What technique do you use to find the direction of the magnetic field?
Right hand grip rule.
- Thumb = direction of current
- Fingers = direction of magnetic field.
What is an electromagnet?
Solenoid with iron core.
[Describe how to] Interpret diagrams of relays to explain how they work.
- Switching on the low-voltage circuit results in a current flowing
- Current activates the electromagnet
- electromagnet attracts the iron block in the high voltage circuit, closing the contacts.
- Current flows through high-voltage circuit.
[Describe how to] Interpret diagrams of doorbells to explain how they work.
- When buzzer pressed, switch closes.
- Current flows in circuit, activating electromagnet.
- Iron contact attracted to electromagnet’s magnetic field
- This causes clapper to move and hit bell, whilst breaking the circuit.
- Iron contact spring back to original position.
