Physics

HideShow resource information
• Created by: h4nss
• Created on: 26-02-15 18:09
Whats a moment and what is it measured in?
The turning effect of a force (Nm)
1 of 23
how can the moment be increased?
By increasing the force, or the distance to the pivot.
2 of 23
What does equilibrium on an object mean?
The sum of all anticlockwise moments is equal to the sum of all clockwise moments.
3 of 23
Describe the characteristics and properties of X-rays?
X-rays are part of the electromagnetic spectrum. They have a very short wavelength and cause ionization.
4 of 23
Explain how the risks from X-ray or CT scanners can be reduced
Precautions such as monitor dose levels, lead shielding, technician leaves room. The lead is used to shield areas of the patients body that aren't being scanned and the exposure time to the X-rays is always kept to an absolute minimum
5 of 23
'ultrasound'
is a sound with a higher frequency than humans can hear
6 of 23
describe how a lens forms an image
lens forms an image by refracting light.
7 of 23
Cornea
Is a transparent 'window' with a convex shape and a high refrative index. The cornea does most of the eye's focusing
8 of 23
Iris
Is the coloured part of the eye. It's made up of muscles that control the size of the puipil - the hole in the middle of the Iris. This controls the intensity of light entering the Eye.
9 of 23
Retina
Images are formed on the retina, which is covered by light-sensitive cells. These cells detect light and send signals to the brain to be interpreted.
10 of 23
explain how total internal reflection occurs
As the angle of incidence increases... refraction of a ray of light from water to air the refracted ray gets closer to the surface of the water. It can only happens when a wave travels through a dense substance towards a less dense substance like
11 of 23
What do we mean by the critical angle of a substance?
The critical angle is the angle of incidence of a light ray in a transparent substance that produces refraction along the boundary.
12 of 23
What is a real image?
A real image is formed by a converging lens if the object.
13 of 23
What is a virtual image?
A virtual image is formed by a diverging lens and, if the object is nearer to the lens than the principal focus, by a converging lens.
14 of 23
How does the eye work?
Light is focussed on to the retina by the cornea and the eye lens, which is a variable focus lens.
15 of 23
What is the centre of mass of an object?
The centre of mass of an object is that point where its mass may be thought to be concentrated.
16 of 23
How does a hydraulic system work?
A hydraulic system uses the pressure in a fluid to exert a force.
17 of 23
How is the size of the force dependant on the angle between the wire and the magnetic field lines?
The force is greatest when the wire is perpendicular to the magnetic field and the force is zero when the wire is parallel to the magnetic field lines.
18 of 23
How do we use the motor effect to make objects move?
An electric motor has a coil which turns when a current is passed through it.
19 of 23
What is a transformer used for?
The alternating pd of the National Grid cables is typically 132,000 volts. A transformer is used to change the size of the alternating pd.
20 of 23
Why do transformers only work with ac?
A transformer only works on ac because a changing magnetic field is necessary to induce ac in the secondary coil.
21 of 23
What is the difference between a step up and a step down transformer?
For a step-up transformer, the number of secondary turns is greater than the number of primary turns. For a step down transformer, the number of secondary turns is less than the number of primary turns.
22 of 23
Why is a CT scan not harmless?
A CT scanner uses X-rays which are ionizing radiation and can therefore damage living tissue.
23 of 23

Other cards in this set

Card 2

Front

By increasing the force, or the distance to the pivot.

Back

how can the moment be increased?

Card 3

Front

The sum of all anticlockwise moments is equal to the sum of all clockwise moments.

Card 4

Front

X-rays are part of the electromagnetic spectrum. They have a very short wavelength and cause ionization.

Card 5

Front

Precautions such as monitor dose levels, lead shielding, technician leaves room. The lead is used to shield areas of the patients body that aren't being scanned and the exposure time to the X-rays is always kept to an absolute minimum