P4 Flashcards
What is magnetic flux density?
It is the measure of the strength of a magnetic field at a specific point in the field.
Give 3 ways to make a solenoid’s magnetic field stronger.
- Insert a soft iron core.
- Increase the current.
- Add more coils.
What is an advantage of using electromagnets?
They can be turned on and off at will.
State the difference between permanent magnets and induced magnets.
P M - have their own magnetic field.
I M - become magnets when put in magnetic fields.
What do magnetic field lines show?
The direction of the field lines from North to South.
The shape of the magnetic field.
The strength of different areas in a magnetic field.
What does the Right Hand rule tell you?
The direction of the magnetic field depending on the direction of the current, and vice versa.
The magnetic field will be anticlockwise if the current is going towards you.
How can you prove a magnetic field exists without using a magnet?
1 - Use a compass. They wi always point to the north pole of a magnet.
2. Iron shavings will take the shape of a magnetic field. Pile them around the suspected magnet and see if they take the shape of the magnetic field.
Give the formula for the force acting on a wire affected by a magnetic field.
Force = length × magnetic flux density × current
Give some examples of permanent magnets.
Cobalt, Iron, Steel and Nickel.
What happens if a wire carrying an electrical current is put into another magnetic field?
The magentic fields add together, which makes them stronger, as two magnetic fields and a direction of electrical current makes a stronger magnetic field. This then exerts a force on the wire, which then makes it move.
What is the motor effect?
A wire carrying an electric current creates a magnetic field. This can interact with another magnetic field, causing a force that pushes the wire at right angles.
State three ways you can make motors run faster.
- Add more coils
- Increase the current
- Use a stronger magnet
What is the generator effect?
When a conducting wire is passed through a magnetic field, a potential difference is then induced. If the wire is in a complete circuit, then a current is induced.
Draw graphs for varying direct current, AC, and DC.
school revision guide pg 40
