Magnetism and Electromagnetism (Paper 2) Flashcards
(21 cards)
When drawing magnetic field lines, which direction should the lines be drawn in?
north to south
What are permanent magnets usually made out of?
steel
Define a dipole
a north and south pole found as a pair
On a magnetic field diagram, if the lines are close together what does this suggest?
the magnetic field is strong
Define induced magnetism
Using permanent magnets to temporarily make an unmagnetised magnetic material a magnet
What is the method for investigating the magnetic field around a current carrying wire?
- battery must be connected to wire to provide current
- switch must be on to provide current
- wooden stand ensures compass is completely horizontal
- place compass next to wire
- compass needle will line up with magnetic field
- use different field strengths by adjusting variable resistor
Define a solenoid
a coil of insulated wire
How is an electromagnet made?
Insulated wire is wrapped around an iron bar. When a current passes through the wire a strong magnetic field is induced, creating an electromagnet
What is a common use for electromagnets?
move car parts across scrapyards
What is the motor effect?
A current-carrying wire in a magnetic field will experience a force which is perpendicular to both the direction of the field and the direction of the current
What is Fleming’s left hand rule?
Thumb and both fingers must all be perpendicular to each other where:
thumb = force
first finger = magnetic field
second finger = current
When the wires are parallel to the magnetic field, what will be the force?
0
In the motor effect, why does the wire rotate?
The opposite forces on each end of the wire are constantly pushing on each end in opposite directions, rotating the wire
How do loudspeakers experience the motor effect?
- electrical current is alternating
- causes magnetic field to alter
- changing attraction and repulsion causes electromagnet to move
- causes the speaker cone to vibrate, producing sound waves
Define potential difference
Energy transferred per unit charge
Define current
Rate of flow of charge
Define resistance
Opposition to the flow of charge
Define electromagnetic induction
When a potential difference is induced across a conductor if there are changes to the magnetic field it experiences
Define the generator effect
If in electromagnetic induction, there is a complete circuit so current is induced also
How can the magnetic fields be changed?
Moving the magnet
Moving the conductor
Give an example of a conductor in electromagnetic induction
a wire
