Electric and Magnetic Fields Flashcards
How is an electric field created?
Around any electrically charged object.
What do magnets produce?
Magnetic field.
What are the two poles?
North and South
How can you show a magnetic field through a drawing?
Magnetic field lines or line of flux with arrows
Where do the lines go from to?
North to South
What does it mean if the lines are closer together?
There is a strong magnetic field.
Where is the magnetic field strongest at?
The poles of magnets
What happens when similar poles meet?
They repel each other
What happens when different poles meet?
They attract each other
What elements are magnetic?
Iron, nickel, cobalt and steel
What is a permanent magnet?
Produce their own magnetic field all the time
What is an induced magnet?
Only produce a magnetic field when in another magnetic field
What is an advantage of induced magnets?
They can be turned off and on
How does current create a magnetic field?
When current flows through a long straight conductor a magnetic field is created
What is the magnetic field around a wire like?
It has concentric circles perpendicular to the wire.
What does the right hand rule show?
It shows the direction of the magnetic field.
What does the thumb represent in the right hand rule?
The direction of the current
What does the fingers that curl in the right hand rule represent?
The direction of the magnetic field.
How is the magnetic field within in a solenoid?
Strong and uniform
It is useful traits of electromagnets?
They are only magnetic when you keep the current flowing in the wire.
It can also be reversed when the current changes direction.
What are the four ways you can increase the strength of an electromagnet?
- Increase the current
- Increase number of turns in the coils
- Decrease length of coil
- Add iron core
What is the motor effect?
A current carrying wire in the presence of a magnetic field will experience a force
What does the thumb represent in the left hand rule?
Direction of the force
What does the first finger represent in the left hand rule?
Direction of the magnetic field
What does the second finger rule represent in the left hand rule?
Direction of the current
What is the formula for force?
Magnetic flux density x Current x Length
F = B x I x L (lower case)
What does step up transformers do?
- Increases the voltage to around 400,000
- Decreases current
- Increase p.d
- More number of coils
- Less energy wasted
What does step down transformers do?
- Decreases the voltage
- Increases current
- Decrease in p.d
- Less number of coils
- Safe for house to use
What do isolating transformers do?
- No change in p.d.
- Used for safety
- isolated from a circuit from the rest of the household current
How is static built up?
- By friction
- certain insulating materials are rubbed together
- negative charge will be scrapped off one onto the other
- ## the material that loses electrons becomes positively charged
How are electrons able to move to create static electricity?
- The material are insulators
- electrons can move
What is the function of a dynamo?
- Generate direct current
What happens in a dynamo?
- the generators apply a force to rotate a coil in a magnetic field
- as the coil spins
- a current is induced
How can you increase the strength of an electromagnet?
- change the current
- increase the number of turns in a wire
What are the factors that affect the size of the force?
- changing current
- changing the strength of magnet
- changing angle between wire and magnetic line
