magnetism Exam Questions Flashcards
Explain how a moving coil loudspeaker produces sound waves (4)
current creates a mag field around the coil which interests wirh the permanent magnetic field. Producing a force causing the coil to move. When the direction of the current reverses the direction of the force reverses.
Why are there slip rings in an alternator?
To provide a continuous contact between the coil and the brushes
When the handle of an alternator is turned the coil rotates. Explain why an alternating current is induced in the coil. (5)
The coil moves cuts through the mag field. A potential difference is induced across the coil along with a current as it is a complete circuit. Every half turn the potential difference reverses direction. So the current changes direction every half turn.
What is the function of a microphone?
To convert sound waves into variations of current
A student pushes a bar magnet ina coil, why does this produce a pd?
coil cuts through magnetic field lines
A student pushes a bar magnet ina coil, why is the induced pd across the coil alternating?
becuz the magnet changes direction
Explain how the loudspeaker converts current in an electrical circuit to a sound wave.
The current in the circuit is varying. As it passes thru the coil the coil experiences a force, reversing current reverses force. Varying current causes the coil to vibrate, this caused the cone to vibrate, which causes air molecules to vibrate. This movement produced pressure variations needed for sound wave
