Physics P3 Fashcards

Holly Bamford
Flashcards by , created over 4 years ago

Finished P3 3.6/3.6 complete flashcard deck for P3 physics

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Holly Bamford
Created by Holly Bamford over 4 years ago
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Question Answer
What do we use X-rays in hospitals for? to make images and C.T. scans to destroy tumours at or near the body surface
Why are X-rays dangerous? they ionise substances they pass through, which can damage them.
What can we say about the absorption of X-rays when they pass through the body? X-rays are absorbed more by bones and teeth than by soft tissues
What is a C.T. scan? C.T. scans distinguish between different types of soft tissue as well as bones and teeth
What are ultrasound waves? sound waves of a frequency above 20 000 Hz
What are ultrasound waves used for in medicine? Ultrasonic scanning Destruction of kidney stones
Why is an ultrasound scan safer than a X-ray? It is non-ionising.
What do we mean by the refractive index of a transparent substance? It is a measure of how much a substance can refract a light ray
How can we calculate the refractive index? sin (i) ____ sin (r)
What do we mean by the critical angle of a substance? the angle of incidence of a light ray in a transparent substance that produces refraction along a boundary
How is the critical angle related to the refractive index of the substance? 1 ----- Sin (c)
What do we mean by total internal reflection? when the angle of incidence is greater than the critical angle.
What do doctors use an endoscope for? to see inside the body directly
What is a converging lens? Convex- focuses parallel rays to a point (principal focus)
What is a diverging lens? Concave- makes parallel rays spread out as if they came from a principle focus.
What is a real image? Is formed if the the object is further away than the principal focus
What is a virtual image? Formed if the object is nearer to the lens than the principal focus
What do we mean by magnification? image height ------------- object height
How can we find the position and nature of an image formed by a lens? a ray diagram can be drawn
How does the eye work? Light is focused on to the retina by the cornea and the eye lens, which is a variable focus lens
What is the range of vision of the human eye? 25 cm to infinity
What do we mean by the power of a lens? P=1/focal length in meters (f)
What is short sight and how do we correct it? Can only see near objects clearly. Use a diverging lens
What is long sight and how do we fix it? Can only see distant objects clearly Use a converging lens
Why is the refractive index of glass important in making spectacle lenses? The higher the refractive index the thinner and flatter the lens can be
what does the moment of a force measure? The turning affect of the force of an object
How do we calculate the moment of a force? F about a pivot = F x d were d is the perpendicular distance from the line of action of the force to the pivot.
How can we increase the moment of a force? increase f or increase d
What is the centre of mass of an object? Were mass may be thought to be concentrated
What can we say about the centre of mass of an object that is suspended from a fixed point? When it is suspended in equilibrium it's centre of mass is directly below the point of suspension
What can we say about the centre of mass of a symmetrical object? Th centre of mass is along the axis of symmetry.
If an object is in equilibrium the sum of the anticlockwise movements about any point equal...? the sum of any clockwise movement about a point
What can be done to increase the stability of an object? increase the base width and lower the centre of mass
What will make a body topple over? if the line of action is outside it's base
An object topples over if...? the resultant moment about i's turning point is not zero
What do we mean by pressure? It is force divided by the area on which the force acts (pascal (Pa))
What can we say about the pressure in a liquid? it acts equally in all directions
How is pressure transmitted in a hydraulic system? Liquid is virtually incompressible, so the pressure in a hydraulics system is transmitted through the oil
What is centripetal force? An object moving in a circle is acted on by centripetal force
What affects the time period of a pendulum? It's length
How do you measure the time period of a pendulum accurately? Measure the average time for 20 oscillations and divide it by 20
What do we mean by magnetic field lines? The line along which a plotting compass points
How do we make electromagnets? A coil of insulated wire wrapped round an iron core 8de6eae1-dab2-4dec-8ade-c12514f1bea5.gif (image/gif)
What are electromagnets used for? scrapyard cranes circuit breakers electric bells relays
What is the motor effect? a force can act on a wire in a magnetic field when we pass a current through the wire
In the motor effect the force is...? -increased if the current of magnetic field strength is increased -at right angle to the direction of the magnetic field -is reversed if the current of magnetic field strength is reversed
How is the motor effect used to make objects move? an electric motor has a coil which turns when a current is passed through it
What is electromagnetic induction? the process of creating potential difference using a magnetic field
how can a magnet be used to induce potential difference across the ends of the conductor? If a conductor cuts the line of a magnetic field a potential difference is induced across the ends of the conductor
How can potential difference be induced if a electromagnet is used instead of a magnet? It has to be turned on to induce a potential difference
Why do transformers only work with ac? because a changing magnetic field is nececssary to induce ac in the secondary coil
What is the core of a transformer made from? an iron ore unless it is a switch mode transformer which has a ferrite core
How does a switch mode transformer differ from an ordinary transformer? it is lighter and smaller it operates on a high frequency
Why are transformers used on the national grid? to step potential difference up or down
What is the transformer equation? 655420e8-c762-4389-bc1f-29dbf14c3e90.jpg (image/jpg)
What is the difference between a step down and step up transformer? for a step up transformer N s is less than N p For a step up transformer N s is greater than N p
What can we say about a transformer which is 100% efficient? Vp*Ip =Vs*Is where Ip=primary current Is=secondary current
How do we use physics in hospitals? We use physics whenever: blood pressure or temp. is measured ECG recordings are taken endoscopes are used scanners are used