Magnetic Fields Flashcards
[ ] can create magnetic fields
Electric currents
What is the definition of a magnetic field?
A magnetic field is a region where magnetic materials and also wires carrying currents experience a force acting on them
Name 2 magnetic materials
Iron and steel
Describe the arrows on field lines on a field diagram
The arrows on the field lines always point from the north pole of the magnet to the south pole.
What do field diagrams represent?
Magnetic fields
When a current flows through a wire…
a magnetic field is creates around the wire
Describe the magnetic field which is create around a wire
Made up of concentric circles with the wire at the centre
Describe the Right-Hand thumb rule
Shows which way the magnetic field goes. (pg 168)
The thumb shows the current (move your thumb to point in the correct direction)
RIGHT HAND
With your fingers in a fist, the direction of the magnetic field is the direction of your fingers from the hand to the finger tip
Describe a magnetic field inside and outside a coil of wire
Inside: Strong and uniform, (goes straight through the coil)
Outside: Just like a bar magnet (in big loops)
What is another name for a coil of wire?
Solenoid
What is the difference between a magnet and an electromagnet around a solenoid?
You can increase the strength of the magnetic field by adding a magnetically ‘soft’ iron core through the middle of the coil - now an electromagnet
Why is an iron core magnetically ‘soft’? Why is this good?
Magnetically soft materials magnetises and demagnetises very easily. So as you turn off the current through the solenoid, the magnetic field disappears - the iron doesn’t stay magnetises.
Why is it useful that an iron core is magnetically ‘soft’?
The iron doesn’t stay magnetised wen you switch off the current therefore the electromagnetic can be used when you need to switch a magnet on and off
Why are electromagnets used in some canes? (3)
1) Magnets can be used to attract ad pick up things made from magnetic materials
2) If an ordinary magnet was used the crane would be able to pick up the ‘stuff’ but then wouldn’t let it go
3) Using an electromagnet means the magnet can be switched on when you want to and attract and pick stuff up, then switched off hen you want to drop it
What else increases the strength of an electromagnet?
Turns of wire, size of current going through them
