Physics P3

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  • Created by: Izzy
  • Created on: 22-05-13 14:59
What are x-rays used for?
to make images of bones (radiograph) , and to destroy tumours at or near the body surface
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What is formed when the object is further away than the principal focus?
A real image
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What is formed when the object is nearer to the lense than the principal focus
Virtual - magnifed (for convergind)
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What is the equation for magnification?
Image height / object height
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What is the equation for the power of a lens? and the unit?
1/focal length in metres, dioptres
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What does the iris do?
Controls amount of light entering the eye?
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What does the cornea do?
Protects eye and helps to focus light on the retina
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What is the blind spot?
The place where the retina is not sensitive to light
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What do the ciliary muscles do?
Attach to the lens and controls the thickness of the lens
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Compare the eye and camera
Eye can vary focus, camera cannot, eye changes lens thickness and camera changes position of the lens, Real, inverted for both, Light sensitive cells on retina, camera has film. Iris controls brightness, camera has aperture
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How does a lens change if the refractive index is higher?
Thinner and flatter
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What is the moment of an object?
The turning effect of the force on an object
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What is centre of mass?
Where mass is concentrated
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Where is the centre of mass?
Along the line of symmetry
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When a suspended object is in equilibrium, where will the centre of mass be?
Directly beneath the point of suspension
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How is the stability of an object increased?
Making it's base wider and lowering the centre of mass
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Why do objects topple over?
Because the line of action of it's weight lies outside the base, causing a resultant moment - turning point is not zero.
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What is pressure measured in?
Pascals
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What is special about pressure in liquids?
It acts equally in all directions
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How does hydraulics work?
The force of the hydraulic system is much greater than the force applied to it
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What is the other name for hydraulics?
A force multiplier
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What 3 properties does an object have when moving in a circle at a constant speed?
velocity directed at a tangent to the circle, velocity changes direction as it moves around, the change of velocity is towards the centre of the circle
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What is this acceleration towards the centre of the circle called?
Centripetal acceleration
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What is the resultant force that acts towards the centre of the circle?
Centripetal force
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What happens to the centripetal force if the speed is increased?
It also increases
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What happens to the centripetal force if the radius is increased?
It also increases
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The greater the mass of the object moving in a circle..
..the bigger the centripetal force
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What is the motion of a pendulum
oscillating motion
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What is the frequency of oscillations?
Number of complete cycles of oscillations per second
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What is the equation for the time period?
TP = 1/Frequency
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What is an electromagnet made of?
Coil of insulated wire wrapped around an iron core
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What happens when a current flows through a wire?
A magnetic field is produced
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How can the size of the force in an electromagnet be increased?
Increased strength of magnetic field, increase current
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When is the force of the electromagnet greatest?
when the wire is perpendicular to the magnetic field
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When if the force of the electromagnet zero?
When the wire is parallel to the magnetic field lines
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When is the direction of the force reversed?
When the direction of the field or current is reversed
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What are some uses of the electromagnet?
Electric motor (Controlled speed of motor by changing current), Loudspeaker (diaphragm made when coil vibrates when AC current passed through)
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What happens if an electrical conductor passes through a magnetic field?
potential difference is induced across the ends of the wire (electromagnetic induction)
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What is the voltage of the national grid?
132KV
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How does a transformer work?
AC current in primary coil - inducing AC magnetic field, continues in the secondary coil producing a potential difference
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Whats the difference between a step up and step down transformer?
Step up, less coils in first, more coils in second. and vice versa
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What is a switch mode transformer?
transformers that operate at high frequencies with a ferrite core, operate at 50-200 KHZ, lighter and smaller - used for mobile phone chargers
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Other cards in this set

Card 2

Front

What is formed when the object is further away than the principal focus?

Back

A real image

Card 3

Front

What is formed when the object is nearer to the lense than the principal focus

Back

Preview of the front of card 3

Card 4

Front

What is the equation for magnification?

Back

Preview of the front of card 4

Card 5

Front

What is the equation for the power of a lens? and the unit?

Back

Preview of the front of card 5
View more cards

Comments

Ash

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Thank You so much! It was very helpful :)

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