random p7 Flashcards
How do transformers work?
When supplied with an alternating current, primary coil will generate an alternating magnetic field
This then induces a magnetic field in the iron core
This induces an alternating voltage in the secondary coil which then leads to an alternating current
Equation for force?
F=BIl
What is the motor effect?
A current carrying wire in presence of a magnetic field will experience a force
What must be done to experience a full force?
Current carrying wire must be placed perpendicular to the magnetic field
When is potential difference generated?
When a wire experiences a change in magnetic field
What would generate a pd in a wire?
Moving either the wire or the magnet
What will happen if the wire moves up and down repeatedly perpendicular to the field?
create an alternating potential difference
What will happen if a wire moves parallel to a field?
Not generate a potential difference
Explain how an electromagnetic induction (generator effect) is used in dynamos.
A coil of wire is turned inside a magnetic field, which induces a magnetic field, and hence current, in the coil of wire. The coil is connected to a commutator which switches the connections every half-turn. This causes the induced current in the external circuit to be in one direction (d.c.).
What is the function of a loud speaker?
Converts electrical signals into sound waves
What is the function of a microphone?
Converts sound waves into electrical signals
What do loud speakers rely on?
Motor effect
What do microphones rely on?
Generator effect
Explain how a moving coil loud speaker produces a sound
current creates a magnetic field (around the coil)
(which) interacts with the permanent magnet field
producing a (resultant) force causing the coil/cone to move
(when the) direction of the current reverses, the direction of the (resultant) force
reverses (producing a sound wave
explain how a moving coil microphone works
sound waves cause the diaphragm to vibrate
the diaphragm causes the wire to vibrate
the wire cuts magnetic field lines
a potential difference is induced
Explain how an electromagnetic induction (generator effect) is used in dynamos.
A coil of wire is turned inside a magnetic field, which induces a magnetic field, and hence current, in the coil of wire. The coil is connected to a commutator which switches the connections every half-turn. This causes the induced current in the external circuit to be in one direction (d.c.).
