# P2B REVISION NOTES

SINGLE SCIENCE, OCR BOARD - HIGHER TIER, PHYSICS - P2B

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Power stations
Power stations produce alternating currents
We can `see' alternating currents using an oscilloscope
The dynamo produces a changing voltage and current

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An oscilloscope shows how the alternating voltage changes
with time
The maximum voltage and the frequency can be found
from the trace
To calculate the frequency
the following equation is
used:
Frequency = 1
period
The unit is hertz, Hz (waves per second)
Calculate the frequency when a wavelength or period is point
0.07m
Frequency = 1
period
= 1
0.07

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The needle on the ammeter moves as the magnet is moved
in and out the coil
Electricity is only generated when the magnet is moving
Mini generators
A bicycle dynamo is small and
electrical generator
A magnet rotates inside a coil of wire
and an alternating current is produced…read more

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There are three ways to increase the current from a dynamo
Use a stronger magnet
Increase the number of turns of wire on the coil
Rotate the magnet faster ­ on a bicycle the means
pedalling faster
The electricity generated in a power station it is transported all
round the country on the national grid
The power station produces 25,000 volts of electricity
However, transmitting power at this voltage also means a high
current which means high resistant and loss of electrical energy