6 MAGNETISM + ELECTROMAGNETISM Flashcards
What do magnetics do to magnetic substances
Attract them
Attraction of like poles
Repel
Attraction of unlike poles
Attract
Where do magnetic field lines run
North to South
Define a magentic field line
The direction of force on a small NorthPole at that point
What is a magnetically soft material
A material that gains and looses magnetism easily
How to draw uniform magnetic field lines
- Straight and with arrows from N -> S
- Close together = stronger force
What is a neutral point of a N-N magnet
- In the centre between field lines, where there is no magnetic field
- Magnetic forces balance (cancel)
How to investigate magnetism with iron filings
- Place magnet on desk, then paper over, and around with pencil marking north pole
- Carefully sprinkle iron filings on top
- Tap the paper to allow them to fall into place
How to investigate magnetism with plotting compasss
- Place magnet on piece of paper and draw around in pencil and mark north pole
- Place plotting paper on compasss
- Draw around plotting compass, and mark direction of arround with ‘x’
- Move plotting compass, so tail of arrow is on ‘x’ and mark direction again
- Repeat to build up field pattern
Unit for current
Ampere (A)
Unit for power
Watt (W)
Unit for voltage
Volt (V)
What happens when an electrical current flows through a conductor
It produces a magentic field around it
How do you increase the strength of an electromagnet
- Add a soft iron core
- Increase the current
- Add more coils
What rule is used to observe the magentic field in a straight wire
Right thumb grip
Why does the middle area of a flat coil have a strong magnetic field
As the fields add
What is the magnetic field of a solenoid
Same as bar magent
* North = current in
* South = current out
What does a CROSS represent on an electromagnetic drawing
Current moving AWAY
What does a DOT represent on an electromagnetic drawing
Current moving TOWARDS you
Describe how the motor effect works
- Magnetic field of bar magnet interacts with the magnetic field created by current in the wire
- Strong field one side where 2 forces add, and weaker where 2 forces subtract
- Wire moves up/down due to motor effect
What must the components of flemming’s left hand rule be at
90’
What must the components of flemmings right hand rule be at
90’
First finger in flemming’s rules
Magnetic Field (North to south)
Second finger in flemming’s rules
Current ( + to - )
Thumb in flemming’s rules
Motion
How can you make an object move faster that’s undergoing the motor effect
Increase current or Stronger magnets
How is current induced
When a wire cuts through a magnetic field
How do you increase current in electromagnetic induction
- Stronger magnets
- Faster Movement
- More coils
- Larger Coils
How does a transformer work
- Pass AC current through primary coil
- Primary coil becomes an electromagnet, creating a changing magnetic field
- Changing field in channelled into secondary coil by soft iron core
- Changing field induces a voltage into secondary coil
Why is electricity transported at a low current, and high voltage
To reduce power loss
Use of step-up transformer
Increase voltage to decrease power loss
Use of step-down transformer
Decrease voltage so appliances aren’t damaged
Transformer equation
Primary Voltage / Secondary Voltage = Primary Turns / Secondary Turns
