P2 - Magnetism & Electromagnetism Flashcards
In what direction do the magnetic field lines always travel?
From north to south
What does it mean if the field lines are closer together?
That the magnetic field is stronger
Define permanent magnet
Produces their own magnetic field
Define induced magnet
Magnetic materials that run into a magnet when they’re put into a magnetic field. When you take away their magnetic field they lose their magnetism.
What happens to a wire when current flows through it?
A magnetic field is created around the wire
How does the Right-Hand Thumb Rule work?
Whatever direction the current is going you point your thumb in that direction with your hand in the thumbs up position. The direction of the circular magnetic field is whatever way your fingers are coiled from your knuckles to the tips of your fingers. For examples if the current was going upwards then you would point your thumb up and the magnetic field would go clockwise, whereas if the current was going down the magnetic field would be anti-clockwise
What is a solenoid?
A coil of wire, this causes the strength of the magnetic field to increase. To increase this even more you can put a block of iron in the solenoid. This is called an electromagnet.
What are the uses of electromagnets?
- Scrap yard cranes to pick things up
- Inside other circuits to act as switches (like in a motor)
What is the motor effect?
When a current-carrying wire is put between magnetic poles causing the magnet and the conductor to exert a force on each other which causes the wire to move.
What does the wire need to do for the motor effect to work?
The wire has to be at 90 degrees to the magnetic field
What is the equation for magnetic flux density?
Force (N) = Magnetic Flux Density (T, Tesla) x Current (A) x Length (m)
How does Fleming’s Left-Hand Rule work?
Put your thumb and index finger in a shooting gun position and then have your middle finger 90 degrees from you index finger.
Thumb = force
Index finger = field
Middle finger = current
If the force was acting upwards you would point your thumb upwards and then you can see what direction the field and current are in
How does a basic DC motor work?
There are two forces acting on the two arms of the coil of wire which is carrying a current. On one side the coil is being pushed up and on the other side it is being pushed down. The split ring commutator reverses the current every half turn causing the coil to be pushed over the other side meaning it will turn in a circular motion.
What is the generator effect?
The induction of a potential difference (and current if it’s a complete circuit) in a wire which is moving relative to a magnetic field or experiencing a change in magnetic field.
How do you make the generator effect happen?
By moving a magnet in a coil of wire or moving a conductor in a magnetic field. This cuts the field lines. Moving the magnet in the opposite direction will cause the potential difference/current to be reversed.
