Magnetism, Electromagnetism, Generation And Transmission Of Electricity Flashcards
What are permanent magnets?
Hold their magnetism for a long period of time and are usually made from steel or the alloy alnico. These materials are Difficult to magnetise but retain their properties.
What are electromagnets?
Temporary magnets. Made from soft iron, which is easy to magnetise but doesn’t retain its properties.
What are the laws of magnetism?
Unlike poles (North and south) attract.
Like poles (north and north/south and south) repel.
What is a magnetic field?
A region around a magnet in which it will exert its influence.
What are magnetic flux lines?
Lines drawn to represent a magnetic field. Always flow from north to south.
The weakest field is furthest away from the poles, and the strongest field is at the poles.
For example of diagram check notes.
What is created when current flows trough a conductor?
Magnetic field.
What is a solenoid?
A long cylindrical coil of insulated wire.
What is the shape and direction of the magnetic field that is created when current flows through a solenoid?
Check notes.
Resembles bar magnet field
What happens to a magnetic field when the current direction is reversed.
The magnetic field is reversed.
What is the right hand grip rule?
If your fingers of your right hand represents the direction the current flows in the coil, your thumb points towards the North Pole.
Describe the experiment that investigates how the strength of the electromagnet is affected by the current, number of turns, and core.
- Set up the circuit as shown above (check notes).
- Record the number of coils of wire.
- Record the current.
- Use an iron nail as the core.
- Close the switch.
- Record how many paper clips can be lifted.
- Change the current.
- Record the new number of paper clips lifted.
- Repeat for various currents.
- Then, keeping the current the same, repeat for different numbers of coils.
- Keep coils and current the same, repeat for wooden and copper cores.
What force is generated when a conductor is placed in a magnetic field.
Thrust. This force is always perpendicular to the field and current direction and is largest when field and current directions are right angles to each other.
What is Flemings left hand rule?
Check notes.
Hold thumb, first finger and second finger at right angles to each other, with thumb pointing ups second pointing straight, and second bent 90 degrees,
This shows the direction of thrust compared to field and current.
Thumb is thrust, pointer is field, middle is current.
What affect does increasing the coil current of the motor have on its speed?
Increases
What affect does increasing the magnet strength of the motor have on its speed?
Increases
