P3 - Exam Mistakes Flashcards
Compare the stability of a tall raft and a low raft. 3 marks
Lower raft is more stable
This raft has a LOWER CENTRE OF MASS
Because this raft is lower
What is dioptres equivalent to?
1 / metres
What do you need to remember in lens diagram?
Put arrowheads on approaching rays and one the emerging rays
What property of a liquid enables a hydraulic brake system to work?
LIQUIDS ARE INCOMPRESSIBLE
Explain why a side arm of a motor experiences a force. 2 marks
The current creates a magnetic field around the wire
So this magnetic field interacts with the magnetic field of the magnets producing a force
A suitcase is held at an angle. Explain why it falls and hits the floor when it is let go. 2 marks
Line of action of the weight is outside the base of the bag
A resultant moment acts on the bag
Explain how an AC in the coil creates an AC in the secondary coil. 3 marks
Changing direction of current in primary coil
Creates a constantly changing magnetic field in the iron core
This magnetic field induces a voltage in the secondary coil
Give 4 advantages of a switch mode transformer
More efficient
Uses little power when it is on
Smaller
Lighter
State one medical use of ultrasound scanning
Pre-natal scanning
State 2 causes of long sight
Eyeball is too short
Lens being unable to focus an image at the retina
What is the retina equivalent of a digital camera?
CCD
What is important when calculating the refractive index?
Answer to one decimal place
Explain why tipping the wheelchair over at a large angle may cause it to become unstable and topple over. 2 marks
Line of action of weight outside the base
So there will be a RESULTANT MOMENT
Why does the ray of light stay within the optical fibre?
Angle of incidence is greater than critical angle
Why would the movement on the wire be up then down for an alternating current?
The force continually changed direction on the wire
