P-7 Electromagnetism and Magnetism Flashcards
What are poles of a magnet
- Places where the magnetic forces are the strongest
- Two like poles repel each other-
- Two alike poles attract each other
- Non- contact force
What happens when two magnetics are brought close to each other
- They exert a force on each other
What does a permanent magnetic produce -
- A permanent magnet produces its own magnetic field
What is a magnetic field
- A region around a magnet where a force acts on another magnet or non magnetic material
- When removed from this field an induced magnet loses all its magnetism
- Depends on distance- strength
What are permanent and induced magnets
- Permanent magnets produce their own magnetic field
- Induced magnets are magnetic materials that turn into magnets when put into magnetic field
- Force between permanent and induced is always positive
How of compasses show the direction of magnetic fields
- Tiny bar magnet.
- North pole is attracted to south pole of any other magnet
- Compass points in direction of magnetic field its in
- -When not in field they point north-core metal
- What is the direction of the magnetic field
- given by direction of force that would act on another north pole placed at point
- Magnetic field line is from the north pole to the south pole of a magnetic
What happens when a current flows through a conducting wire
- A magnetic field is produced around the wire
- Strength depends in the current and distance
- What happens when a wire is shaped to form a solenoid
- Increase in strength in magnetic field by a current through a wire
- Strong and uniform
- Similar magnetic field to bar magnet
What is a solenoid
- Coil of wire where increased strength of magnetism can be seen
why does a solenoid’s structure produce a stronger field
- This is as field lines around each loop line up
- Lots of field lines in same direction- very close- stronger
What happens when you add an iron core to a solenoid
- Increases the strength
- Becomes induced magnet when current is flowing
What is an electromagnet
- A solenoid with an iron core
What is the motor effect
- When a conductor carrying a current is placed in a magnetic field the magnet producing a field and conductor exert a force on one other
- Conductor placed between magnets
- How does the full force be experienced in the motor effect
- Wire has to be at 90oc to magnetic field
- if parallel it will experience no force
- Increases with amount of current that passes through
- Increases with strength of current passing through
What is the equation to find the force seen in the motor force - Given
- F= B x I x L
- Force = Magnetic flux density x current x meters
What is magnetic flux density
- How many field lines there are in a region
- What is flemmings left hand rule
- How do find the direction of a force
- How do you use Flemming’s left hand rule
- Using left hand, point first finger in direction of field
- Point second finger in direction of current
0- Thumb will then point in direction of force
What does lemmings left hand rule show
- Either a current or magnetic field is reversed, then direction of force will be reversed
- Represents relative orientation of the force, current in the conductor and magnetic field
What is the basis of a electric motor
- COIL of wire carrying a current in a magnetic field that tends to rotate
- How does a magnetic field cause rotation
- Forces act on two side arms
- Because coil is in spinal;e forces act one up one down- this causes it to rotate
- Split running communICATOR IS A WAY OF SWAPPING TJE CONTACTS EVERY Half turn to keep it turning gin one direction
- Can be changed direction by switching the poles
How can the speed of an electric motor e increased
- Increasing the current, adding more turns to coil or increasing magnetic field density
- Can use Left hand rule to work out witch way it will turn
