Physics Unit 3 (P3) essential notes

heyy, i looked over the past papers for this unit and picked out the essential things for each topic, hope it helps! good luck in exams 2morrow!

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  • Created on: 26-05-11 11:07
Preview of Physics Unit 3 (P3) essential notes

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What is an ultrasound?
A sound wave above 20,000 Hz
What does the term media mean?
The materials through which sound travels
What can be calculated from the time intervals between two different media?
The distance between the boundary and the detector (object)
What action should scientists take if they find evidence that ultrasonic waves are harmful?
They should publish their evidence, or tell a doctor, or carry out more research to make
What happens to ultrasound when it reaches the boundary between two different media and
is NOT reflected?
It is absorbed and transmitted
Explain how sound waves clean jewellery
The particles vibrate and knock particles of dirt off the jewellery
Explain why different pulses occur
The sound waves are reflected. The pulses indicate cracks and the end pulse indicates
where the back of the crack is
Explain why taking results several times and then calculating the average is more reliable than
taking only a single result
So the data can be compared and anomalous results can be identified and checked.

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Why is the core made of iron?
So it becomes magnetised
Why is insulated wire used to make the coils?
To prevent a short circuit
How does a transformer work?
1. An alternating current in the primary coil
2. Produces a changing magnetic field in the core
3. Hence magnetic field is in the secondary coil
4. Which induces an alternating potential difference across the secondary coil
5.…read more

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Explain how a generator works
1. Coil cuts through the magnetic field
2. A potential difference is induced
3. The coil is part of the circuit
4. The potential difference (p.d) causes a current in the circuit
5. Slip rings and brushes enable the coil to be connected without twisting the
Explain why a varying p.d is induced across the coil even when the rate of flow of oil
remains constant
The magnetic field cuts through the coil. P.…read more

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What is meant by the period of a plant?
The time for a planet to go around the sun
What is the force, which provides the centripetal force to keep the planets in orbit?
The sun's gravitational force
Explain why the solar system was formed from material produced when earlier stars
Solar system contains heavy elements. These elements were formed by nuclear fusion at a
very high temperature in a supernova
Acceleration changes the DIRECTION but not the SPEED.…read more


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