Formal assessment section 3 Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

theextension of an elastic object is ___________ to the force applied , provided that the ___________ is not exceeded

A

directly proportional

limit of proportionality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what must happen to change the shape of an object?

A

more than one force must be applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does elastically deformed mean?

A

when an object returns to its original shape after the forces are removed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what does inelastically deformed mean?

A

when an object does not return to its original shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what happens when the limit of proportionality for the extension of an elastic object and applied force has been exceeded? (3)

A
  • doubling the force will no longer exactly double the extension
  • the relationship becomes non-linear
  • a force-extension graph will stop being a straight line
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the equation for , extension , force, and spring constant

A

force= spring constant x extension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is spring constant?

A

it indicates how easy it is to stretch or compress a spring- the higher the spring constant, the stiffer the spring.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

when is the work done on the spring and the elastic potential energy stored not equal

A

when the spring is inelastically deformed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do Loudspeakers work?

A

1) when a current flows through the coil, both the coil and the speaker core experience a force due to the magnetic field. The speaker core moves
2) Because the current is alternating when the direction of the current through the coil reverses, so too does the direction of the force exerted on it and the speaker core
3) this causes the speaker core to vibrate back and forth, producing a sound wave
4) the air around the core also vibrates creating variations in pressure that cause a sound wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do scrapyards work?

A

Scrap vehicles are lifted in a scrap yard using powerful electromagnets attached to cranes

when the current is turned on, the electromagnet attracts magnetic material below it

when the current is turned off, there is no more magnetic force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do circuit breakers work?

A

this is a switch in series with an electromagnet, held by a spring

when the current is too large, the switch is pulled open by the electromagnet and it stays open until it is reset manually

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do electric bells work?

A

1) When the switch is pushed, the electromagnet is magnetised
2) The electromagnet attracts the armature
3) The hammer strikes the gong and breaks the circuit
4) the armature springs back, completing the circuit again and remagnetising the electromagnet
5) the cycle repeats for as long the button remains pushed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do relays work?

A

Relays are used to switch an electrical machine on or off

1) a small current through the coil of the electromagnet magnetises the iron core
2) this pulls the armature onto the electromagnet, whose other end pushes the contacts together, completing the circuit.
3) When the current is switched off, the contacts open again, switching the circuit off.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do microphones work?

A

1) Sound waves hit a flexible diaphragm that is attached to a coil of wire, wrapped around a magnet

2) This causes the coil of wire to move in the magnetic field, which generates current
* the diaphragm oscillates due to the changes in air pressure related to the sound wave

3) The microphone diagram and coil vibrate at the same frequency as the incoming sound. The bigger the amplitude of the sound, the bigger the amplitude of the vibration
4) this induces a potential difference and current in the coil with the same frequency of the incoming and wave and an amplitude dependent on the amplitude of the incoming wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a convex lens?

What happens in a convex lens?

A

lens that curves outwards

rays of light are brought to a focus at the principal focus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the focal length?

A

The distance from the lens to the principal focus

17
Q

Why doesn’t the middle ray get refracted?

A

because it is normally incident onto its surface

18
Q

What is a concave lens?

What happens in a concave lens?

A

lens that curve inwards

parallel rays of light entering the lens spread out, this makes the rays of light appear to have come from the principal focus on the same side of the lens they have originated

19
Q

What type of images do convex lenses?

What type of images do concave lenses?

A

real or virtual

only virtual

20
Q

What is a real image?

A

on the opposite side of the lens to the object can be projected onto a screen

lens come together

21
Q

What is a virtual image?

A

on the same side as the object and can only be seen by looking through the lens

lens dont come together

22
Q

equation for magnification

A

image height/ object height

23
Q

How to make a lens more powerful?

A
  • making the focal length more powerful
  • make the lens more curved
  • use different material that naturally refract light strongly
24
Q

What happens to the image when an object is more than 2 focal lengths from the convex lens?

A
  • image is diminished
  • inverted
  • the image is real
25
Q

What happens to the image when an object is between 1-2 focal lengths from the convex lens?

A
  • magnified
  • inverted
  • real
26
Q

describe what happens to light when it passes through a lens

A

it refracts :

the light bends towards the normal when it passes into the lens

then away when it passes out of the lens

27
Q

What happens to the image when an object is reflected by a concave lens?

A
  • diminished
  • right way up
  • virtual ( rays do not meet at the principal focus)
28
Q

What happens to the image when an object is closer to the lens than the focal length for a convex lens?

A
  • virtual image
  • magnified
  • right way up

this is why convex lenses are used as magnifying glasses

29
Q

required practical 9 light box

A

1) Set up a ray box, slit and lens so that a narrow ray of light is produced.
2) Take an A3 paper and draw a straight line down the centre using a rule.
3) Use a protractor to draw a second line at right angles to this line. Label this line with an ‘N’ for ‘normal’.
4) Place the longest side of a rectangular acrylic polymer block against the first line. With the normal near the middle of the block, carefully draw around the block without moving it.
5) Turn off all the lights in a ray and. Use the ray box to shine a ray of light at the point where the normal meets the block. This is the incident ray.

The angle between the normal and the incident ray is called the angle of incidence.

6) Using a pencil on the paper, mark the path of:
the incident ray, the reflected ray and transmitted ray with a cross

7) Remove the block. Join the crosses to show the paths of the light rays.

8) Repeat steps 2 to 7 for a rectangular glass block.
Measure the angle of incidence, angle of refraction and angle of reflection for each block.