Alternator
The coil cuts magnetic field lines
A potential difference is induced (across the coil)
There is a complete circuit, so a current is induced (in the coil)
Every half turn the potential difference reverses direction
So (every half turn) the current changes direction
Dynamo
The sides of the coil (parallel to the magnet) experience a force (in opposite directions)
The forces cause moments that act in the same (clockwise / anticlockwise) direction
(each half-revolution) the two halves of the (rotating) commutator swap from one (carbon)
brush to the other
(each half-revolution) the commutator reverses the current (in the coil)
How the loudspeaker converts current in an electrical circuit to a sound wave
A cone with a wire wrapped around it is connected to an a.c power supply and is placed in a
permanent magnetic field
The current passes through the coil
When current flows through the wire, it creates a
Second magnetic field, which interacts with the permanent field
The coil experiences a force (inwards or outwards)
Reversing the current reverses the force
The size of the current affects the size of the force
The varying current causes the coil to vibrate
The (vibrating) coil causes the cone to vibrate
The vibrating cone causes the air molecules to move
The movement of the air molecules produces the pressure variations in the air needed for a
sound wave
The coil cuts magnetic field lines
A potential difference is induced (across the coil)
There is a complete circuit, so a current is induced (in the coil)
Every half turn the potential difference reverses direction
So (every half turn) the current changes direction
Dynamo
The sides of the coil (parallel to the magnet) experience a force (in opposite directions)
The forces cause moments that act in the same (clockwise / anticlockwise) direction
(each half-revolution) the two halves of the (rotating) commutator swap from one (carbon)
brush to the other
(each half-revolution) the commutator reverses the current (in the coil)
How the loudspeaker converts current in an electrical circuit to a sound wave
A cone with a wire wrapped around it is connected to an a.c power supply and is placed in a
permanent magnetic field
The current passes through the coil
When current flows through the wire, it creates a
Second magnetic field, which interacts with the permanent field
The coil experiences a force (inwards or outwards)
Reversing the current reverses the force
The size of the current affects the size of the force
The varying current causes the coil to vibrate
The (vibrating) coil causes the cone to vibrate
The vibrating cone causes the air molecules to move
The movement of the air molecules produces the pressure variations in the air needed for a
sound wave
