| Induced Potential & the Generator Effect | 1- Electromagnetic Induction(Generator effect): A coil of wire is moved into a magnetic field, a magnet is moved into a coil of wire.
2- Induced voltage produces an induced current (if conductor is connected in a complete circuit). The induced current creates a magnetic field around itself, this magnetic field opposes the original change
3- Current is reversed when: magnet is moved out of coil, other pole of magnet moves into coil
4- Induced PD will increase if: speed of movement increases, magnetic field strength increases, no. of turns on a coil increases |
| AC Generator | - a device that produces a potential difference
- Consists of a coil of a wire rotating in a magnetic field
- As one side of the coil moves up through the magnetic field, a potential difference is induced in one direction, as the rotation continues and that side of the coil moves down, the induced potential difference reverses direction ∴ the current is constantly changing
- maximum PD or current can be increased by:
- increasing the rate of rotation
- increasing the strength of the magnetic field
- increasing the number of turns on the coil
graph looks like this: ~~~~ |
| DC Generator | - another device that produces a potential difference
- consists of a coil of wire rotating in a magnetic field
- uses a split ring commutator rather than the two slip rings found in ac (eg, bike lights use Dynamo)
Maximum PD or current can be increased by:
- increasing the rate of rotation
- increasing the strength of the magnetic field
- increasing the number of turns on the coil
The graph looks like this: nnnnnn |
| Microphones | - Sound waves into electrical signals, use the generator effect to induce a changing current from the pressure variations of sound waves
MOVING-COIL MICROPHONES:
1) pressure variations in sound waves cause the flexible diaphragm to vibrate
2) the vibrations of the diaphragm cause vibrations in the coil
3) the coil moves relative to a permanent magnet, so a potential difference is induced in the coil
4) the coil is part of a complete circuit, so the induced potential difference causes a current to flow around the circuit
5) the changing size and direction of the induced current matches the vibrations of the coil
6) the electrical signals generated match the pressure variations in the sound waves |
| What's needed to make an electric current flow in a circuit? | PD |
