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Y8 EOY > physics > Flashcards

physics Flashcards

1
Q

Why does a light bulb transfer energy to its
surroundings?

A

A bulb transfers energy to the surroundings by light waves and heating when a current flows through it because
the filament wire gets hot.

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2
Q

Why does a light bulb get hot when a current
flows through it?

A

Electrons collide with the atoms inside it. These collisions happen because the filament wire has a property called resistance and we call the collision process resistive heating.

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3
Q

Why are resistors useful components in
electric circuits?

A
  • keep the current at safe levels
  • heating devices
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4
Q

What is voltage?

A

a measure of the energy transferred to (or from) the electrons

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5
Q

How is voltage measured? What does the
measurement tell you?

A

Voltage is measured with a voltmeter, the unit is volts.
It tells us how much energy was transferred

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6
Q

How does the voltage across the battery relate to the voltage across the components in a series circuit?

A

The voltage across the battery equals the total voltage of all of the components.

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7
Q

What would the current voltage graph look
like for a resistor?

A

It would be a straight line through the origin. Because for a resistor voltage is directly proportional to
current.

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8
Q

What would the current voltage graph look
like for different resistors?

A

The larger resistance the steeper the line would be on the graph because when the same current flows through a larger resistance more work will have to be done by the electrons

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9
Q

What is resistance measured in?

A

Resistance is measured in ohms (Ω)

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10
Q

How do you calculate the resistance of a
resistor?

A

Reistance = Voltage / Current (R = V/I)

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11
Q

What is acceleration?
What is deceleration?

A

Acceleration is the rate that an object speeds up.
Deceleration is the rate an object slows down.

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12
Q

What is the unit for acceleration?

A

m/s/s

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13
Q

What does a speed time graph tell
us?

A
  • A straight line tells us that the object is moving with constant acceleration.
  • The steeper
    the line on a speed time graph the larger the object’s acceleration.
  • A flat line on a
    speed-time graph tells us the object is moving at a constant speed.
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14
Q

What happens to an object when a resultant force acts on it in the direction it is moving?

A

It accelerates and it’s kinetic store increases.

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14
Q

What happens to an object when a resultant force acts on it in the direction it is moving?

A

It accelerates and it’s kinectic strore increases.

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15
Q

What is the relationship between the size of an object’s acceleration and the resultant force acting on it?

A

Acceleration is directly proportional to resultant force.

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16
Q

What does a graph of acceleration
against resultant force look like?

A

It would go straight through the origin

17
Q

What happens to an object when a resultant force acts on it in the opposite direction to its motion?

A

It will decelerate - its kinetic store will decrease and the thermal store of the surroundings will increase

18
Q

When you push an object, and then let go, why does it slow down?

A

there is a resultant
force acting on it in the opposite direction to its motion; like friction

19
Q

How do we stop moving vehicles?

A

We apply brakes, to apply a force in the opposite direction.

20
Q

Why do we stop moving vehicles
over a longer period of time?

A

As smaller deceleration’s require smaller resultant forces.

21
Q

Why do objects moving through air experience air resistance?

A

As the object collides with the air molecules.

22
Q

Why do larger surface areas and faster speeds result in more air resistance?

A

The larger the surface area of the object and the faster it is moving the more air molecules it will collide with per second

23
Q

What forces act on a falling object?

A

air resistance and weight

24
Q

What is terminal velocity?

A

When the falling object reaches a steady speed

25
Q

Why do falling objects reach
terminal velocity?

A

the air resistance force will equal the weight and at this point there will be no resultant force so the object cannot accelerate any further

26
Q

What energy transfers take place in an object falling at terminal
velocity?

A

its gravitational store is
decreasing, the kinetic store stays the same and the loss from the gravitational store is transferred to the thermal store of the surrounding.

27
Q

What energy transfers take place in an object falling at terminal
velocity?

A

its gravitational store is
decreasing, the kinetic store stays the same and the loss from the gravitational store is transferred to the thermal store of the surrounding
.

28
Q

How do we see things?

A

because light from that object reaches the retina at the back of our eyes

29
Q

What is the normal line?

A

The normal line is a dashed line drawn at 90 degrees to the surface of an object

30
Q

What is the law of reflection?

A

the angle of incidence = the angle of reflection

31
Q

What is the difference between diffuse and specular reflection?

A
  • Specular reflection happens when light is incident on smooth surfaces. Parallel rays of incident
    light are reflected in a predictable way and remain parallel to each other upon reflection.
  • Diffuse reflection happens on rough surfaces. Parallel rays of light do not remain parallel to each other on reflection and are scattered in different directions.
32
Q

What is a virtual image? Why is it
different to a real image?

A

A virtual image is one which the light rays appear to come but don’t actually come from the
image e.g. the image seen in a mirror.
A real image is one where the light rays do come from.

33
Q

What is refraction and why does it
happen?

A

It happens because
materials have different densities. It causes the wave to change
direction.

34
Q

What effects does the refraction of light lead to?

A

Refraction of light at water/air boundaries causes objects to appear closer to the water than they actually are.

35
Q

What happens to parallel rays of light when they enter a convex lens?

A

They converge to the focal point

36
Q

What happens to parallel rays of light when they enter a concave lens?

A

They diverge away from the lens

37
Q

How are lenses used to correct eye defects?

A

They help the light focus on the retina. Short sighted - concave
long sighted - convex

38
Q

What happens to white light when it is shone through a prism?

A

The seperate colours of the spectrum are seen

39
Q

What is the electromagnetic spectrum?

A

A family of transverse waves.
R, M, I, V, U, X, G

40
Q

What are electromagnetic waves used for?

A

R - communication M - cooking I - security U - florescent light X - medical imaging G - sterilising

41
Q

Why are UV, X rays, and gamma rays dangerous?

A

Damage the structure of DNA.

Y8 EOY (13 decks)

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