Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Module 4 paper 2 > Flashcards

Module 4 paper 2 Flashcards

1
Q

Define current

A

rate of flow of charge

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

define 1 coulumb

A

the flow of carhe in a time of 1 second when the current is 1 ampere

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

how is a current produced in a metal

A

In a metal, there is a lattice of positive ions, surrounded by free electrons. The
positive metal ions are fixed in place, but the electrons can move around, and so when one side
of the metal is made positive, and the other side is made negative, the electrons will be attracted
to the positive side, and move through the metal as electric current

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

how is a current produced in an electrolyte

A

ionic sollution, when a pair of electrodes are placed in the cations and anions split and are attracted to the electrodes producing a flow of charge

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

kirchhoffs first law

A

at any point in an electrical circuit, the sum of the currents in the junction is equal to the sum coming out that junction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

define mean drift velocity

A

is defined as the average velocity of the electrons as they travel down the
wire, colliding with positive metal ions

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

define potential difference

A

is used to measure the work done by charge carriers, which lose
energy as they pass through the components in a circuit. It is defined as the energy transferred
from electrical energy to other forms, per unit charge

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

define electromotive force

A

used to measure the work done to charge carriers, when they gain
energy as they pass through a cell or power supply. It is defined as the energy transferred from
chemical energy to electrical energy per unit charge,

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

what is an electron gun and how does it work?

A

used to produce a thin beam of electrons, which are accelerated to
high speeds. A small metal filament, which acts as a cathode, is heated by passing a potential
difference through it. Some of the electrons in the metal gain enough kinetic energy to escape the
metal, in a process known as thermionic emission. The circuit is in a vacuum tube, with a high
p.d., V, between the filament and the anode, so the freed electrons are accelerated towards the
anode. If the anode has a small hole in it, a beam of electrons can pass through at a specific
kinetic energy.

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

how to calculate the velocity of an electron

A

ev = 1/2mv^2

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

define resistance

A

potential difference across a component divided by the current in it

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

ohms law

A

for a metallic conductor kept at a constant temperature the current in the wire is directly proportional to the potential difference across it

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

why does ohms law not apply to some components

A

when the current across the component increases, the metal ions are
heated, gaining kinetic energy and vibrate more around their fixed points in the metallic lattice.
This increases the frequency of collisions with electrons, so more work is done on the charge
carriers, increasing the resistance

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

current against voltage graph for component that obeys ohms law

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

current against voltage fraph for filament

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

determine resistivity

A

First, the
cross sectional area of the wire is recorded, by taking multiple readings with Vernier callipers at
different points along the wire, and taking an average. Then, a circuit is set up using a recorded
length of the wire, with a voltmeter connected in parallel and an ammeter in series. The values
for p.d. and current can be recorded to determine the resistance of the wire, and used along with
the length and cross sectional area to determine the resistivity of the material the wire is made
from

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

define electrical powert

A

rate of energy transfer and tis measured in watts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

kirchoffs second law

A

in any circuit the sum of the electromotive force is equal to the sum of the potential difference in a closed loop

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

internal resistance and lost volts

A

not all of the energy transferred
to the charge carriers is available to the circuit, as some is transferred to the internal resistance of
the cell. This results in a difference between the measured p.d. across the terminals of the power
supply, and the actual e.m.f. of the cell, which is referred to as the ‘lost volts’, and is equal to the
p.d. across the internal resistor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

determine internal resistance

A

To determine the internal resistance of a cell, the cell with internal resistance r is connected in
series to an ammeter and a variable resistor. A voltmeter is connected in parallel around the cell.
The resistance of the variable resistor is varied, and the V and I readings recorded. The equation 𝜀 = 𝑉 + 𝐼r is rearranged to 𝑉 = 𝜀 − 𝐼r. When a graph of terminal p.d. (V) against current (I) is
plotted, the y intercept of the graph will be the e.m.f. of the cell and the negative gradient will
be the internal resistance of the cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Potential divider circuits

A

From Kirchhoff’s second law, we know that in a series circuit the current is constant, and the p.d.
splits in a ratio proportional to the resistance of each component By considering the ratio of the resistance for one component with the total circuit resistance, we
can determine the potential difference across this component, using the formula

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

define progressive wave

A

an oscillation that travels transfers energy from one place to another without transferring matter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

define transverse wave

A

wave osciallations occur perpindular to the direction of travel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

define logintude wave

A

wave oscialltions occur perpindular to the direction of travel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

define amplitude

A

maximum displacement from equilibrium position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

phase difference

A

difference in displacement of particles along a wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

phase difference

A

difference in displacement of particles along a wave

27
Q

determine frequency

A

an oscilloscope is fed a signal, usually using a
microphone. The timebase on the oscilloscope can be set on the x axis to represent time and on
the y axis to represent the amplitude. The time taken to complete one full oscillation can be
measured, and then used to find the frequency.

28
Q

reflection

A

occurs when a wave changes direction at a boundary between two media,
remaining in the original medium The angle
of the incident ray to the normal of the boundary between the two media is the same as the angle
of the reflected ray to the normal. The wavelength and frequency of the wave remain the same.

29
Q

Refraction

A

when a wave changes direction as it changes speed, when it enters a new
medium. In the new medium, the frequency of the refracted waves remains constant, but the
speed of the wave changes The wavelength of the wave changes as a result There will always be some
partial reflection at the boundary between the two media

30
Q

Diffraction

A

spreading out of a wave front as it passes
through a gap. The wavelength and frequency of the wave are
not altered. Maximum diffraction will occur when the gap the
wave passes through is the same size as the wavelength of the
incident wave

31
Q

Polarisation

A

unique to transverse waves. It occurs when the oscillation of a wave
is restricted to one place only – this type of wave is said to be plane polarised. Longitudinal
waves cannot experience polarization, as the direction of energy transfer is already in one plane
only, whereas in transverse waves, the oscillations occur in many planes, at right angles to the
direction of travel

32
Q

technique to demonstrate refraction and diffraction

A

A ripple tank can be used to demonstrate wave properties. A wave is made using an oscillating
paddle connected to an electric motor. The depth of the tank can be adjusted to show refraction.
A slit can be added to show diffraction

33
Q

technique to demonstrate polarization

A

To demonstrate polarization of microwaves, a metal grille can be used. A microwave transmitter
and receiver are placed on opposite sides of the grille, and microwaves are transmitted which are
plane polarized with the electric field oscillating in the vertical plane. With the metal grille in the
vertical orientation, the microwaves can pass through it and the maximum signal will be
received. As the grille is rotated around to the horizontal orientation, the signal received will
fall to a minimum, as the vertically plane polarized microwaves will be absorbed by the free
electrons within the metal bars of the grille, greatly reducing transmission

34
Q

define intensity of a progressive wave

A

defined as the radiant power passing at right angles
through a surface per unit area I = P/A
A = 4πr^2
he intensity of the light is therefore inversely proportional to the square
of the radius. The intensity of a wave can also be related to the amplitude of the wave,
Intensity ∝ Amplitude^2.

35
Q

Electromagnetic wave

A

transverse progressive waves, consisting of magnetic and electric
fields which oscillate at right angles to each other. They can travel through a vacuum, and all
travel at the speed of light

36
Q

The refractive index,

A

n, can be used to determine the angle of refraction in to the
medium.
n = c/v

37
Q

snells law

A

n1sinx1=n2sinx2

38
Q

Total internal reflection

A

occurs at a boundary between two transparent media, with no refraction
– all of the light incident on the boundary is reflected back in to the original medium.
Firstly, the light must be travelling
from a material with a higher refractive index, to a material of lower refractive index. Secondly,
the angle of incidence of the ray to the normal must be above the critical angle

39
Q

critical angle

A

sinc = 1/n

40
Q

The principle of superposition

A

when two waves meet at a point, the resultant
displacement of the wave at that point is equal to the sum of the displacements of the individual
waves

41
Q

coherent

A

Two waves are coherent when they are emitted with a constant and unchanging phase
difference

42
Q

Interference

A

the superposition occurring between two coherent
waves.

43
Q

maxima

A

. When two coherent waves interfere, the maximum resultant displacement occurs when
the phase difference is an even multiple of π, so the two crests of the wave combine.

44
Q

minima

A

occurs when the phase difference is an odd multiple of π, so
one crest and one trough act to cancel each other out.

45
Q

Techniques to investigate superposition

A

sound waves, two audio signal generators can be used to investigate superposition. They
will both emit coherent waves in all directions, which will overlap and form an interference
pattern. When a microphone connected to an oscilloscope is moved parallel to the speakers,
regions of loud and quiet noise will be detected.

46
Q

Young double-slit experiment

A

used to investigate superposition in light, and also to
determine the wavelength of the light source used. A laser which produces monochromatic light
(light of a single wavelength) is placed behind a sheet with two small slits in it, a distance ‘a’
apart. The two coherent waves produced by the slits overlap and superpose, creating alternating
bright (maxima) and dark (minima) fringes on a screen. The distance between two adjacent
maxima is ‘x’, and the distance between the double slits and the screen is ‘d’.

47
Q

Techniques to investigate wavelength

A

A
diffraction grating is a piece of transparent material with many opaque lines scratched in to it.
The light is able to pass through the transparent slit between the scratches, and produces and
interference pattern with bright and dark maxima and minima. The number of slits is usually
given per cm, and this must be converted in to the value ‘d’, the distance, in metres, between
each slit. The order of maxima (whether it is the original, first, second etc. bright maxima) is
referred to as ‘n’, and θ is the angle between the 0th and nth maxima.

48
Q

Stationary waves

A

formed when two progressive waves with the same frequency (and
ideally the same amplitude), travelling in opposite directions, superpose. The stationary wave
formed has a series of alternating nodes and antinodes

49
Q

Nodes

A

are points which always have zero
amplitude, Two
adjacent nodes are half a wavelength apart.

50
Q

antinodes

A

are points which always have maximum displacement

51
Q

Producing stationary wave on string

A

produce a stationary wave in a stretched string, the string is held taught over a pulley. A
vibration generator is used to oscillate the string in a coherent manner, with the frequency
being adjusted until a stationary wave is produced. The initial wave produced is reflected at the
pulley and, producing two waves with the same frequency, travelling in opposite directions,
which superpose to make a stationary wave. The transmitter and pulley ends will be nodes, with
a node-antinode pattern along the string.

52
Q

produce a stationary wave with microwaves

A

a microwave transmitter can be used to
produce a wave, which is reflected off a metal plate. The incident and reflected waves superpose
to make a stationary wave. A microwave receiver can be moved between the transmitter and the
plate and will observe a minima, maxima pattern

53
Q

Stationary waves producef with sound

A

A tuning fork is used to
produce a loud sound, and is then held over the end of the tube. The length of the tube can be
adjusted (e.g. by placing one end in water) until a stationary wave is produced. The stationary
wave formed will vary depending on the air column – if the column is open at both ends, then
there will be an antinode at each end, but if the column is open at one end only, then the open
end will have an antinode, and the closed end will have a node.

54
Q

fundamental frequency

A

e stationary wave is the lowest frequency of
vibration for a given arrangement. When the wave vibrates at this frequency, it is called the first
harmonic.

55
Q

The photon model

A

, it interacts as discrete energy quanta (‘packets’)

56
Q

plancks equation

A

energy, E, of a photon is directly proportional to the frequency, f, of the electromagnetic
radiation 𝐸 = ℎ𝑓

57
Q

Using LEDs to estimate the value of the Planck constant

A

LEDs only emit light when
the potential difference across them exceeds the threshold p.d. required. A potential divider is
set up to vary the voltage through the LED. A small black tube is placed over the LED, to make
it obvious when the LED has lit up. By varying the p.d. across the LED, we can determine the
threshold p.d., V, required to turn it on. As the LED produces light of a specific colour, we know
the wavelength of the light. Each photon from the LED is emitted when a single electron loses
energy. By equating the energy of an individual electron in the LED with an individual photon
produced, we can use the equation eV = hc/λ to determine the Planck constant.

58
Q

The photoelectric effect

A

When electromagnetic radiation is shone on to a metal, electrons are released from the surface
of the metal.

59
Q

photoelectric effect can be demonstrated using a gold leaf electroscope

A

a zinc plate on top
of a negatively charged stem, with a negatively charged piece of gold leaf attached to the stem.
Initially, the gold lead and the stem have the same charge, so they repel each other. If UV light is
shone on to the zinc plate, free electrons will be released from the surface of the plate, and the
negative charge will slowly be lost, so the gold leaf will gradually fall back to the stem

60
Q

gold leaf electroscope experiment is carried out, several observations can be made

A

type of electromagnetic radiation shone on to the plate is varied. When visible light is
used, it does not matter how intense the radiation is, no electrons will be removed from the
plate. When UV light is used, even if it is a very low intensity, electrons are instantaneously
removed from the plate. These observations are a result of the particulate nature of photons, and
cannot be explained by the wave model of electromagnetic radiation.

61
Q

The work
function

A

φ, of a metal is the minimum energy required to free an electron from the surface of
the metal. Each photon must have energy at least as great as the work function to release an
electron. As the photon’s energy is directly proportional to its frequency, there is a threshold
frequency for the electromagnetic radiation, which is the minimum frequency required to free
electrons from the surface of the metal.

62
Q

Einstein’s photoelectric equation

A

ℎ𝑓 = 𝜙 + 𝐾𝐸𝑚𝑎𝑥
It is a maximum because some electrons may be closer to the nucleus,
requiring more energy than the work function amount to be released, leaving less energy left
over as kinetic energy.

63
Q

increasing the intensity of the radiation

A

will
increase the rate of electron emission. This is because the increase in intensity increases the
number of photons available to interact with the electrons. The only way to increase the kinetic
energy of the electrons is to increase the frequency of radiation further above the threshold
frequency, so there is more energy left over to be converted to kinetic energ

64
Q

The de Broglie equation

A

De Broglie realised that all matter can
exhibit both wave and particle properties, and that the wavelength associated with a particle is
inversely proportional it its momentum, 𝑝
𝜆 = ℎ/𝑝

65
Q

wave-particle duality

A

electromagnetic
waves having a dual nature

66
Q

wave-particle duality

A

electromagnetic
waves having a dual nature

Physics (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions