Topic 7 Flashcards
Magnetic field inside a solenoid
Strong and uniform
Magnetic field around a solenoid
Like that of a bar magnet
Increasing strength of magnetic field of solenoid
Add iron core
Electromagnet
Solenoid with an iron core
Loudspeakers
Convert variations in current to pressure using motor effect
Generator effect
When electric conductor moves relative to magnetic field or vice versa, potential difference produced across conductor
Induced current creates magnetic field that….
Opposes the original change (movement of conductor or change in magnetic field)
Generate ac
Alternator
Generates dc
Dynamo
What is in dynamo to make dc
Split ring commutators change direction of current every half turn
What alternators have to make ac
Brushes and slip rings so contacts don’t swap
Microphones
Use generator effect to convert pressure variations in sound waves into current variations
Why iron used in transformers
Easily magnetised
How solenoid increases magnetic effect of current
Field lines around each loop line up and lots in same direction
The closer the lines together the stronger the field
Things that affect size of force on conductor
Magnetic flux density (how many field lines in the region)
Size of current
Length of conductor in magnetic field
2 things that strength of magnetic field around wire depends on
Current
Distance from wire
How loudspeakers work
Alternating current sent through wire attached to cone
Current uses motor effect causing force which moves cone
Alternating current causes opposite direction so cone moves in alternating direction
Creates variations of pressure in air causing sound waves
Frequency of sound wave same as of ac
What an induced current always does
Creates magnetic field that acts against the change that made it eg movement of wire or change in magnetic field
How to increase size of induced potential difference
Increase speed of movement
Increasing strength of magnetic field
Transformers
Change size of potential difference of an alternating current
Transformer: what induces alternating pd in secondary coil
Changing magnetic field as iron core magnetises and demagnetises
Generator effect caused by either
Moving
Change in the magnetic field (transformers)
