Magnetism and electromagnetism Flashcards
What is a permanent magnet?
A magnet that produces it’s own magnetic field
What is an induced magnet?
Magnetic materials that turn into a magnet when they’re put into a magnetic field
How does a compass work?
Inside is a bar magnet; the north pole is attracted to the south pole of any magnet near which means that it points in the direction of any magnetic field, including the earth’s own one, which is why a compass always points north
What happens when a current flows through a wire?
A magnetic field is produced around the wire, made up of concentric circles perpendicular to the wire
How can the strength of a magnetic field be effected?
The larger the current is or the closer to the wire you are, the stronger the magnetic field
What is a solenoid?
A coil of wire
How can a solenoid be used for a magnetic field?
By wrapping the wire into a solenoid, the strength of the magnetic field is increased as the field lines around each loop of wire line up with each other, meaning that there are lots of field lines pointing in one direction
How can you increase the field strength of a solenoid?
By putting a block of iron in the centre as it turns into an induced magnet (this is called an electromagnet) or by adding more coils to it
Why are electromagnets useful?
They only work when a current is flowing through the solenoid, meaning they can be turned on and off, which a permanent magnet can’t
What are the main uses of electromagnets?
In scrap yards to pick up then release certain metals and within other circuits to act as switches
What is the motor effect?
When a current carrying wire is put between magnetic poles, the magnetic field around the wire interacts with the magnetic field it has been placed in. This causes the magnet and the conductor to exert a force on each other
How can the wire experience the full force during the motor effect?
The wire has be at 90 degrees to the magnetic field as the force always acts at right angles to the magnetic field and the direction of the current in the wire
How does the force acting on the wire become increased?
If the strength of the magnetic field is increased or if the current running through the wire is increased
How do you find the size of the force acting on a wire?
Magnetic flux density x current x length
Which fingers represent what in Fleming’s left hand rule?
The thumb is force, the first finger is field and the second finger is current