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what is induced voltage?
A voltage is induced in a conductor whenever the conductor moves in a magnetic field, or, if the conductor remains stationary, the magnetic field changes.
What are simple a.c. generators called?
what can transformers be used for?
to change the magnitude of an a.c. voltage
what does a transformer consist of?
two coils of wire wrapped around a soft iron core
parts of a dynamo are:
- iron core
- stator coil
in a dynamo, what is the rotor?
- a permanent magnet.
- when this rotates there is a voltage induced in the stator coil
what does the size of the induced voltage in a dynamo depend on?
- strength of the magnetic field
- number of turns on the coil
- relative speed of motion
in a full-sized generator what does the rotor and stator do?
- the rotor uses an electromagnet instead of a permanent magnet to produce a stronger magnetic field.
- the stator also consists of several coils in order to generate large currents
what happens in electrical transmission?
- transformers are used to reduce power losses in electrical transmission.
- this is done by operating the transmission lines at a high voltage.
in the National Grid, what are step-up transformers used for?
- to increase the voltage from the power station.
- overhead lines then carry electricity round the country
- step-down transformers are then used to reduce the voltage to suitable levels for industries and homes
why are transformers not 100% efficient?
- energy can be lost
- heat losses in coils
- magnetising/ demagnetising losses
- eddy currents in the core
- sound losses
why is energy lost as heat in a transmission line?
- due to the resistance of the line
- to reduce the current and therefore the power losses, the voltage is stepped-up