1
Q
What is current? What is it measured in and how?
A
- flow of charged particles
- measured in Amps (A) using an ammeter connected in series with the component
2
Q
What is voltage? What is it measured in and how?
A
- a measure of the difference in energy between one part of a circuit and another
- measured in Volts (V) with a voltmeter that is connected in parallel with the component
3
Q
Explain current and voltage in series
A
- series circuits have only one loop
- only one path for current
—> A1=A2=A3 - voltage adds to supply
—> V1=V2+V3
4
Q
Explain current and voltage in parallel
A
- multiple loops called branches
- voltage is the same across all branches
—> V1=V2=V3 - sum of currents in each branch is equal to supply
—> A1=A2+A3
5
Q
Define resistance (including equation)
A
- measure of the opposition to current low in an electrical circuit
—> ohms
R=V/I
6
Q
Explain resistors in series
A
- sum of all individual resistances
- adding components in series increases total resistance in a circuit
R=R1+R2
7
Q
Explain resistors in parallel
A
- adding components decreases the total resistance
1/R=1/R1+1/R2
8
Q
Draw the IV graphs for lamps
A
9
Q
Draw the IV graphs for wire
A
10
Q
Draw IV graphs for diode
A
11
Q
Describe a thermistor and draw the symbol
A
- thermal resistor - resistance changes with temp
- resistance decreases as temperature increases
12
Q
Describe an LDR and draw the symbol
A
- light dependant resistor
- resistance of LDR decreases as light intensity increases
13
Q
Define power and give the 3 equations
A
- energy transferred in seconds, measured in watts
P=E/t
P=VI
P=I^2R
14
Q
How do fuel based power stations work?
A
- chemical energy stored in fuel is converted to heat energy
- heat is used to heat water and produce steam
- steam turns turbine which is connected to generator
- generator turns and produces energy
15
Q
Energy pathway for nuclear and fuel power stations
A
Fuel: chemical -> heat -> kinetic -> electrical
Nuclear: chemical -> heat -> kinetic -> electrical
16
Q
Percentage efficiency equation
A
Energy usefully transferred
————————————— x100
Energy supplied
17
Q
What is the national grid?
A
- network of cables that connects every power station to every home, shop, factory, school, hospital and every other customer
18
Q
How does the national grid ensure a reliable supply?
A
- supplying electricity from another power station if one breaks down
- monitoring power use ad responding to changing demand
19
Q
What is meant by the base load?
A
- electricity produced continually by power stations that cannot quickly change their output
- NG provides >base
- HEP short start time so used to provide additional energy at peak times
20
Q
What do transformers do?
A
- change voltage
- step up increase voltage before transmitted through cables ( decreased current decreases heat loss to increase efficiency )
- step down reduce voltage to make safer for customers
21
Q
Define density and give the equation
A
- how much mass is in a volume of material
D=mv
V=lwh
22
Q
Explain conduction
A
- heat moves from hot to cold
- particles vibrate more vigorously when heated and collide with nearby particles, transferring some energy
- repeats until heat transferred from hot to cold side
—> metals conduct heat best due to free electrons
23
Q
Explain convection
A
- liquid and gas
- hot water rises and cold water down creating a convection current
- particles gain energy when heated and move more vigorously so volume increases and density decreases
- less dense air rises and colder sinks
24
Q
Payback time equation
A
Installation cost
————————
Annual saving
25
Why is insulation beneficial?
- less heat lost per second so lower energy bills
- less energy consumption so less fossil fuels so less CO2 so less global warming
26
What determines the cost of an electrical appliance?
- its power
- length of time used
- cost of each unit of energy
27
2 equations for cost of electricity
Units used (kWh) = power x time
Cost = units used x cost per unit
28
Why are appliances connected in parallel?
- lamps brighter as all the same voltage
- if one breaks, others still work
- ability to switch lamps on individually
29
Advantages of ring main circuit
- cables can be thinner as 2 paths for current
- each part of cable carries less current as flows 2 ways
- ring main circuit convenient as sockets placed anywhere
- each socket has 230V
30
Uses of the live, natural and earth wire
Live: carry current to appliance at high voltage
Neutral: complete circuit and carry away at low voltage
Earth: safety wire to attach to metal casing which carries current safely to the ground
31
Explain fuses, MCBs and RCCB
- safety devices
- fuse: wire breaks if current too high
- MCBs: stop if current too high using electromagnet to open switch
—> automatically reset
- RCCB: protects the user
—> sensitive and reacts quickly
—> reset easily
32
Wave speed equations
Wave speed = wavelength x frequency
33
Define longitudinal and transverse waves
Longitudinal: particles move parallel to propagation of waves
Transverse: particles move perpendicular to propagation of wave
34
Speed of water in deep and shallow water
Deep = quick
Shallow = slow
35
Draw refraction
36
Draw reflection and label angles
37
Electromagnetic spectrum
Radio. — longest wavelength, lowest freq & energy
Microwave
Infrared
Visible
UV
X-ray
Gamma ray. — shortest wavelength, highest freq & energy
38
Describe geosynchronous and geostationary satellites
Geosynchronous: orbit time of 24hrs - return to same position above earth once every day
Geostationary: orbits above the equator at the same point at all times. Communicate using microwaves. 36000km
39
Conditions for TIR
- angle of incidence > critical angle
- waves move from dense to less dense
40
When the angle of incidence is equal to the critical angle, the angle of refraction is…
90 degrees
41
What are optical fibres?
- thin rods of glass that carry info as pulses of light that rely on TIR to operate
42
Endoscope vs CT
- endoscope is a long, think, flexible tube that uses optical fibres to produce images of body
—> invasive
- CT scans use x-rays to produce general 3D images
—> non-invasive, higher risk than endoscopy, ionising
43
What are earthquakes?
- release of energy in the form of seismic waves
- point of origin is below the earths surface called the focus
- point waves arrive first, then s then surface
44
Characteristics of P waves
- longitudinal
- fastest
- solid + liquid
45
Characteristics of S waves
- transverse
- slower
- solids
46
Characteristics of surface waves
- transverse + longitudinal
- slowest
- surface only
47
Draw the structure of the earth
48
Draw the P and S wave paths
49
What is pressure?
- force per unit area
p=F/A
50
Impact of surface area and force on pressure
- increased surface area = decreased pressure
- increased force = increased pressure
- decreased surface area = increased pressure
- decreased force = decreased pressure
51
Relationship of pressure and volume, inc graph
- pressure is IV to volume
- gas particles exert force on container when collide so decreased volume increases number of collisions
- increased rate of change of momentum leads to increased force so increased pressure
P1V1=P2V2
52
Relationship between temperature and pressure, inc graph
- increased temp = increased pressure
- more collisions due to increased KE so greater rate of change of momentum therefore more force so more pressure
- DP when temp in Kelvin
P1. P2
— =
T1. T2
53
Overall volume, temp and pressure equation
P1V1. P2V2
——- =. ———
T1. T2
54
Define specific heat capacity
- amount of heat energy required to increase the temp of 1kg of a substance by 1 degrees
Q=mcdeltaT
55
Define specific latent heat of fusion
- amount of heat energy needed to change the mass of 1kg of a substance from a solid at its melting point into a liquid at the same temp
56
Define specific latent heat of vaporisation
- amount of heat energy required to change 1kg of a liquid at its boiling point into a vapour without a change in temp
Q=mL
57
Draw the SLH graph
58
Define a magnetic field
- area around an Brecht where a magnetic force can be measured
—> lines always N to S
—> strength shown by spacing of lines
59
Draw MF around wire and a coil
60
What is each finger in Flemings left hand rule?
- thumb = motion
- pointer = field
- ring = current
61
Factors impacting the size of force
- size of current
- strength of magnetic field
- length of wire in field
62
MF and force equation
F=BIl
63
Role of split ring and carbon brush in simple DC motor
Split ring: ensures the force on one side of the coil is always up and the other is always down
Carbon brush: ensures there is connection between power supply and split ring
64
Explain electromagnetic induction
- if a wire is moved through a magnetic field it will cause a current to flow
65
How can the size of current induced be increased?
- increasing strength of MF
- increasing speed of movement
- increasing length of wire within MF
- increasing speed of rotation
- adding turns to coil
66
What hand rule is used for a generator and motor?
- left hand for motor
- right hand for generator
67
How do transformers work?
- alternating current flows through P coil
- creates alternating MF around P coil
- soft iron core becomes magnetised and strengthens MF and connects to S coil
- alternating current now flows in S coil
—> laminated iron core to reduce energy and increase efficiency of transformer
68
How do you identify step up and step down transformers?
Step down: more coils on P than S
Step up: more coils on S than P
69
Transformer equation
V1. =. N1
—- —-
V2. N2
70
Define scalar and vector
Scalar: magnitude only
Vector: direction and magnitude
71
Define thinking and braking distance
Thinking: distance vehicle travels when driver is reacting
Braking: distance vehicle travels after brakes applied
72
Factors affecting thinking distance
- tried
- drugs/alcohol
- distraction
- speed of vehicle
73
Factors affecting braking distance
- condition of brakes
- condition of tyres
- condition of road
- mass of vehicle
- speed of vehicle
74
What is the benefit of reduced speed limit and seatbelts?
- reduced speed limits reduce the kinetic energy and forces in the impact
- seat belts reduce forces on the body as they stretch and increase the time for a person to come to a stop which reduces deceleration
75
Describe inertia
- resistance to a change in motion
—> increases as mass increases
76
N1
An object will remain at rest or in uniform motion unless acted upon by an external resultant force
77
N2
F=ma
The acceleration of an object is directly proportional to the resultant force and inversely proportional to the mass of an object
78
Difference between weight and mass
Weight: force of gravity acting on an object
Mass: amount of matter in an object
79
Equation for weight
W=mg
80
N3
When body A exerts a force on body B, body B exerts an equal but opposite force on body A
81
Define work and give the equation
- energy transferred
W=Fd
82
Energy types and law of conservation of energy
Motion = KE
Position = GPE
Deformation = elastic energy
—> total energy must remain constant
83
Relationship between force and extension, including equation
- dp
—> increased force = increased extension
- increasing extension increases elastic energy in spring
F=kx
84
How do you calculate the work done in stretching a spring?
- area under Fx graph
W=1/2Fx
85
KE and GPE equation
KE = 1/2mv^2
GPE = mgh
86
4 ways to improve car efficiency
- reducing aerodynamic losses due to air resistance
- rolling resistance due to friction between tires and road
- idling losses due to engine using fuel when vehicle stationary
- inertial losses due to fuel used when accelerating
87
How to reduce aerodynamic, rolling, idling and inertial losses
- streamlined designs
- correctly inflated tyres
- stop start systems
- use lighter materials
88
Momentum equation
P=mv
- vector
89
Define N2 in terms of momentum, including equation
- the force acting on an object is equal to the rate of change in momentum of the object
Force = delta p
———-
Time
90
Define the law of conservation of momentum
- the total momentum before and after an interaction are equal, provided that no external forces are acting on the object
—> if KE is not conserved, then it is an inelastic collision
91
SUVAT equations
V=u+at
X=ut+1/2at^2
X=1/2(u+v)t
v^2=u^2+2ax
92
Define a moment, the equation and the principle of moments
- turning effect of a force
Moment = force x distance
- for a body in equilibrium, the sum of clockwise = the sum of anticlockwise about the same point
93
Planet order (4 rocky, 4 gaseous)
Mercury, Venus, earth, mars, asteroid belt, Jupiter, Saturn, Uranus, Neptune
94
Define a moon, asteroid and comet
Moon: body that orbits a planet
Asteroid: small rocky object that orbits the sun
Comet: lump of frozen gas, rock and dust that orbits the sun
—> tail points away from sun
95
Define a planetary system, galaxy, astronomical unit and light year
- a star and all the objects which orbit it
- huge collection of billions of stars and their solar systems
- mean distance from sun to earth
- distance light will travel in a year
96
Life cycle of a low mass star
- formed from clouds of gas, hydrogen, helium and dust
- protostars form when gravity collects cloud together and heats it up
- in main sequence stars, hydrogen fuses to from helium. This creates enough radiation and gas pressure to balance gravitational forces
- hydrogen runs out and fuse helium into larger elements (ie carbon) to increase G+R pressure. Expand to a red giant
- helium runs out and reaction slows. G+R pressure decreases. Shrink to white dwarf
97
Life cycle of a high mass star
- formed from clouds of gas, hydrogen, helium and dust
- protostars form when gravity collects cloud together and heats it up
- in main sequence stars, hydrogen fuses to from helium. This creates enough radiation and gas pressure to balance gravitational forces
- hydrogen runs out, fuses helium to larger elements (iron) which increases G+R pressure, expand to supergiant
- helium run out. Star explode to supernova. High pressure and temp lead to fusion of heavy elements
- remaining matter collapse to form neutron star or black hole
98
Explain the origin of the solar system
- formed from collapse of cloud and dust
- heavier elements ejected in supernovae
- gravitational forces pulled matter closer
—> hence rocky planets form closest to sun
99
Explain red shift
- increase in wavelength of light as it travels through an expanding universe to reach the earth from distant galaxies which stretches the waves
- the further away a galaxy is, the greater the red shift
- recession velocity increases with the distance of galaxy
—> implies all galaxies originated from same point
100
Explain CMBR
- cosmic microwave background radiation
—> spread of microwaves from all directions
- remains of energy released by Big Bang - started as gamma but stretched to microwaves as universe expanded
101
Define an isotope
- toms of an element that have equal numbers of protons but different numbers of neutrons in their nuclei
102
Define half life
- time taken for the number of radioactive nuclei to reduce to one half of its initial value
103
Characteristics needed for radioactive tracers
- consider HL and the bio impact
- detailed images of body when detector detects radiation emitted in body
104
Characteristics needed for treating cancer
- strongly ionising and moderately penetrating
- also use a source outside of body which would need to be very penetrating and weakly ionising with a long HL
105
Describe nuclear fission
- splitting of a large nucleus into smaller nuclei, releasing energy
—> induced by absorption of slow neutrons
106
Explain how nuclear fission reactors work, including uses of control rods and moderators
- heat released heats water
- steam rotates a turbine that turn a generator to produce electricity
Control rods: absorb neutrons to ensure reaction is controlled and sustainable
—> lowering slows down RoR
Graphite moderator: slows down fast moving neutrons to allow absoportion
107
Describe nuclear fusion
- 2 small nuclei fuse together to create one larger nucleus
- lots of energy needed as repulsion by 2+ve nuclei must be overcome
108
Unit of potential difference
Watt per amp
109
Unit of potential difference
Watt per amp
110
Unit of potential difference
Watt per amp
111
Resistance is directly proportional to …. And inversely proportional to ….
- length of conductor
- cross sectional area
112
What does a higher amplitude mean?
Louder sound
113
What does a higher frequency mean?
Higher pitch
114
Explain the Doppler effect
- when there is relative motion between a source of waves and an observer, the wavelength and frequency detected by the observer is different to that received when there is no relative motion
—> toward observer: increased frequency and decreased wavelength
—> away from observer: decreased frequency and increased wavelength
115
Potential difference equation
Pd = IR
Power = Pd x I
116
Current flowing through a branch in parallel is…
Dependant on resistance
117
Relationship between resistance, length of conductor and cross sectional area
Resistance is dp to length and ip to cross sectjon
118
Relationship between current, voltage and resistance
Current decreases as voltage decreases so resistance decreases
119
What happens to fluid as temp increases?
Expands
120
Frequency equation
1 / time
121
Speed, frequency and time equation
v = wavelength
——————
time period
BMSAT
flashcards
Decks in class (4)
# Cards
