Electromagnetism Flashcards
(17 cards)
What is a magnetic field?
A magnetic field is the area around a magnet where a magnetic material will experience a force.
Where around a bar magnet is the strongest?
The strongest place around a bar magnet is where the field lines are closest together and the weakest is where they are further apart.
What are field lines?
Field lines are what show the direction of the force that would be exerted on another north pole at that point. They are directed north to south.
What happens when two magnets are brought close together?
Opposites poles attract like poles repel.
What is the difference between a permanent and induced magnet?
A permanent magnet produces it’s own magnetic field whereas an induced magnet becomes a magnet when it is placed in a magnetic field.
How can you show the magnetic field of a bar magnet?
Place a magnet in the middle of a sheet of paper, then sprinkle iron filings on the sheet and they should line up with the field lines of the magnet.
How can you plot the magnetic field of a bar magnet?
Place the bar magnet in the middle of a sheet of paper, then place a plotting compass around the magnet, see where the needle points and place the compass at the tip of the needle. Repeat this process until a magnetic field line is formed.
How is a magnetic field produced around a wire?
When a current flows through a conducting wire a magnetic field is produced around the wire.
How can you remember what a magnetic field looks like?
The corkscrew rule says that if you use your right hand and point your thumb in the direction of the wire and curl your fingers, the curled fingers represent the field lines.
What does the strength of a magnetic field around a current depend on?
The strength of the magnetic field depends on the current through the wire and the distance from the wire.
How else can you increase the strength of a wire?
If you shape a wire as a solenoid the strength of the magnetic field will increase.
How can the magnetic field of a solenoid become stronger?
If you add an iron core the strength of a solenoid’s magnetic field will increase. This is called an electromagnet.
Describe the motor effect
When a conductor carrying a current enters a magnetic field the magnet producing the field and the conductor exert a force on each other.
Describe Fleming’s left hand rule
FFS (Force Field Current). Hold your fingers at 90 degrees of each other with your thumbs representing force, index finger representing the field and your middle finger representing the current.
How could you increase the size of the force on a motor?
To increase the force on a motor you can increase the current, increase the magnetic field strength or increase the length of the coil by adding more turns.
How does a motor rotate?
A coil in a magnetic field carries in two opposite directions. One side of the coil experiences a force and the other side experiences a force in the opposite direction. With an axle through the centre of the coil it will rotate.
