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Physics Electricity Topic 2 Flashcards

1
Q

Only ———- can be transferred to and from an atom. A charged atom is called an —–

A

electrons
ion

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2
Q

Two static electricity rules please state them :

build up static is caused by ——–
when certain ———- materials are rubbed together ——— charged electrons will be scraped off one and dumped on the other.
This will leave the materials ——– charged with a ———- static charge on one and an equal ———- static charge on the other.f

A

Opposite charges attract.
Like charges repel.

friction
insulating
negatively
electrically
positive
negative

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3
Q

A van de Graaff generator is like
because it
it was orginally used
it uses ?

A

an industrial version of rubbing a balloon on a jumper, transferring electrons from one place to another. It was originally used to accelerate electrons to very high speed.
it uses to insulators and rubs them together to create a static charge

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4
Q

A force field is caused by ————- these forces do not need to be …

A

non-contact forces
do not need to be in physical contact (touching) for an interaction of forces to take place. Attraction/repulsion of static charges is an example of a non-contact forces.

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5
Q

Electric field lines flow away

A

from positive charges and towards negative charges.

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6
Q

The closer together the field lines are, the
they’re always at —— angles to the surface
how can sparking be explained via electrical fields

A

the stronger the field.
right
sparks are caused when there is a high enough pd between charged object and the earth
a high pd causes a strong electric field between the charged object and the earthed object
the string electric field causes electrons in the air particles to be removed known as ionisation
air is normally an insulator but when it is ionised it is much more conductive so a current can flow through it this is the spark

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7
Q

The strength of the field depends on two things:

A

The size of the charge.
The distance away from the charge

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8
Q

the bigger the charge the bigger ———–
too much static causes ——–
as the —— charge builds on an object the potential difference between the object and the earth ——-
If the potential difference gets —— enough than ——— can jump across the gap between the charged object and the ——- this is the ——-
They can also jumped onto any earthed ———-

A

jump it can make

sparks
electrical
increases
large
electrons
earth
spark
object

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9
Q

charge (c)=
the size of current is the rate of flow of —–

A

current (A) * time (s)
charge

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10
Q

what is electrical current ?
Current will only flow around a circuit if there is a ——————
unit of current: ampere, A

A

electrical current is the flow of electric charge round the circuit.
potential difference

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11
Q

In a single, closed loop the current has the same ————
everywhere in the circuit -

A

value

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12
Q

multiple cells=

A

battery

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13
Q

what 2 things are needed for current to flow?

A

something to make electricity flow - a cell battery or power pack

a complete path for the current to flow

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14
Q

equation for charge

A

Q=I*T
charge measured in coulombs
=current measured in Amps * time the flow of electrons measured in seconds

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15
Q

electric charge
what is it measure in?
what is it carried by?

A

measured in coulombs is carried by electrons and gives rise to electric current when allowed to move around a circuit

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16
Q

Electric current
what is it measured ?
How is it measured?

A

measured in Amps is the rate of flow of a charge in a circuit . The size of an electric current is the amount of electric charge passing any point in a circuit per second

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17
Q

electrons transfer energy to components around

A

a circuit . For example electrons can transfer energy from a cell to a bulb

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18
Q

Ammeters measure ——— and are connected in ——-

A

current
series

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19
Q

Voltmeters measure —————— and are connected in ————

A

potential difference
parallel

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20
Q

The potential difference (voltage) between two points in a circuit is include units of measurement

A

the work done or energy transferred J per Coulomb of charge that passes between points

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21
Q

potential difference equation(involvingcurrent)
:

A

potential difference (v)= current (A) * resistance (omega symbol) (ohms)

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22
Q

the greater the resistance across a component

A

the smaller the current that flows through it

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23
Q

The resistance of ohmic conductors does not ——- with the current at a constant —— the current flowing through an ohmic conductor is ———- proportional to the potential difference across it
The resistance of some resistors and components does change e.g——————–
When an electrical charge flows through a filament lamp it transfers some energy to its ———– energy store which is designed to ———— resistance increases with ——— so as the current increases the filament lamp heats up more and the ———- increases.
For diodes resistance depends on ——— they will happily let current flow in one ———but will have a very high ———– if reversed.

A

change
temp
directly
filament lamp or diode
thermal energy store
heat up
temp
resistance
direction
direction
resistance

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24
Q

Potential difference equation with work and charge

A

v=w/q

potential difference (V)=
work j/charge (C)

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25
electrical resistance is
the opposition to the flow of charge
26
resistance is measured in what is the symbol
a unit called OHMS omega Ω is the symbol for OHMS
27
what in a circuit causes resistance?
the electrons flowing through a circuit have to push through lots of vibrating ions which resist the passage of electron flow
28
what elementsin a circuit decreases/increases resistance?
length of wire heat type of material diameter or cross section of wire
29
a resistor is a device a resistor is anything that -------
A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit slows down the flow
30
If you have two resistors in parallel their total resistance is equalt ot half the resistance of onr of the two resistors why is this:
How does this affect the whole circuit?In parallel both have same pd across them as the source this means the 'pushing force' making the current flow is the same as the source pd for every resistor that you add But by adding another loop the current has more than one direction to go in this increases the total current that can flow around the circuit using V=IR an increase in current means a decrease in the total resistance of the circuit .
31
potential difference current and resistance equation what is this equation called
V=I*R potential difference in volts = current in amps * resistance in OHMS OHMS LAW
32
what is OHMS law ?
the current through a conductor ( at constant temperature ) is directly proportional to the voltage across two points therefore by OHMS law if the current doubles then so will voltage
33
as the ammeters changes position in the circuit the current ---------
stays the same
34
as the number of bulbs increases, the resistance --------- this causes current to --------
increases decrease
35
As the potential difference increases, the current ------ this makes the bulbs -------
increases brighter
36
the potential difference at the power source is split across each of the components in a series circuit. Another way of saying this is that :
the p.d across each component added together make the p.d of the power supply
37
what happens to the current in a parallel circuit?
the current is split between each 'loop' of the parallel circuit, such that theoretical current from the power. Supply is equal to the sum of the currents in each loop. In fact the current is split in each loop in 'inverse proportion' to the resistances of components in the loop (ie. if loop 1 had a higher resistance than loop 2) it has lower current and vice versa)
38
multiple resistors in a series cause the -------------------------- to increase
overall resistance
39
# (think of the properties of the wire) resistance in a wire increases as it gets
longer or thinner
40
adding more batteries increases the ---------- and the bulbs become ---------
current brighter
41
adding more bulbs decreases the ----------- and the bulbs become ------------
current dimmer
42
the resistance of components such as thermistors and LDR's is
not constant it changes with the current through the component
43
the resistance of some types of a thermistor ------------------ as temp increases they make useful
decreases temp detectors e.g. car engine temp sensors and electronic thermostats
44
the resistance of an LDR ------------------ light intensity increases They uses are
decreases as automatic night lights, outdoor lighting and burglar detectors
45
how would the resistance of a wire change depending on temp
as the wire heats up , just like all other particles of matter - they gain kinetic energy and begin to vibrate this vibration increases the resistance to the flow of current . therefore the current should go down
46
conductors
allow electrons to flow : there are plenty of free electrons allowing a material to do this
47
insulators electrons?
prevent the flow of electrons there is an absence of free electrons and so there struggles to be a current
48
semi-conductors
have electrons but in order for them to become 'free' energy needs to be supplied to them. this can be in the form of heat or light
49
thermistor what is it made of how does this affect it?
a device for which resistance will vary depending on temperature a thermistor is made of a semi-conducting material and as such , as it becomes hotter , electrons can become free
50
electrons flow out of the negative terminal and towards the --------------- terminal
positive
51
DC is definition and examples
direct current the current flows in one direction only examples: cells and batteries
52
ac definition and examples and what is frequency
alternating current alternating pd in which the positive and negative ends keep alternatinghe current constantly changes direction, how often it does is called 'frequency' examples mains supply from a pocket socket
52
amplitude is the
height of the wave
53
wavelength
length between two troughs
54
mains electricity volts and frequency
230 volts and 50 hertz frequency
55
what does it mean if a supply is 30 hertz
this means that the current flow changes direction and back again , 30 times per second
56
frequency equation =
1/time period (s)
57
why does touching the live wire give u an electric shock: your body just like earth is at -- V This means that if you touch the live wire a large potential difference is produced across your body and a ---------- ------- through u this causes a large electric shock that could: even if a plug socket or live wire is turned off (e.g the switch is ----) there is still a danger of an ----------------- a current isnt flowing but there is still ------ in the live wire.
0 current flows injure , kill open shock pd
58
electrical apliances are designed to transfer energy to components in a ------- when a ----------- ------- a good example is the kettle it... of course no appliance transfers all energy completely usefully the higher the ------ the more energy is transferred to the energy stores of components
circuit current flows transfers energy electrically from the mains ac supply to the thermal energy store of the kettlr of the heating element inside kettle current
59
In a parallell circuit each component is -------connected to the +ve and -ve supply (except ammeters which are always connected in ------). If you remove or disconnect one of them it will -------- effect the others at ----- This is obviously how most things must be connected, for example in cars and in household electronics. You have to be able to switch everything on and off --------
seperately series hardly all separetely mixture
60
In parallel circuits all components get the full source ----- so the voltage is the ----- across all components In parallel circuits the total ------- flowing around the circuit is equal to the total of all the currents through the seperate -------- In a parallel circuit there are junctions where the current either ----- or rejoins the total current going into a junction has to ------ the total current leaving it If two identical components are connected in parallel than the same -------- will flow through each -------------
pd same current component
61
safety design on plug
a fuse is connected between live pin and live wire the fuse wire melts it too much current passes through it . This means that the live wire is cut off
62
what happens if the live wire touches the nuetral wire
a very large current will rush between both wires this is called a short circuit if the fuse(A glass or ceramic canister containing a thin wire that melts if the current gets too high) breaks it will blow the circuit
63
nano watt
0.00 000 0001
64
micro watt
0.00 0001
65
milli watt
0.001
66
mega watt
1 000 000
67
gigga watt
1 000 000 000
68
power equation
power in watts= energy in joules divide / time in seconds
69
power in watts= you can also found power if you don't know the potential difference
potential difference (V) * current in amps p= i squared r where i is current r is resistance and p is power
70
The national grid uses a : why is this : Pylon cables made of
high pd and a low current to transmit the high amount of power needed you either need a high pd or high current the problem with high current is that you lose loads of energy as the wires heat up and energy is transferred to the thermal energy store of the surroundings. Its much cheaper to boost the pd up really high (to 400 000 V) and keep current relatively low for a given power increasing the pd decreases the current which decreases the energy lost by heating the wires and the surroundings. this males the national grid an efficient way of transferring energy very thick aluminium
71
what is the journey of electricity from power station to your home
power station , step up transformer(the pd is increased, cables and pylons(with huge insulators), step down transformer, home
72
transmitting eletricity at high voltage does what? the total energy transferred by an appliance depends on : the power of an apliance is the the energy it transfers per ------
it reduces energy loss and makes the system more efficient. how long its been on for and its power second
73
# does what? step up transformer
increases the voltage decreases the current more turns on secondary coil
74
step-down transformer
decreases the voltage increases the current less turns on secondary coil
75
how can an object become negtive or positively charged
by gaining or losing electrons
76
positive ions are and negatives are
cations anions
77
# (detailed) what happens when two oppositionally charged objects move closer together
When 2 oppositely charged objects come close together this can cause electrons in the air molecules to be pulled towards to + object . If the f ield is strong enough it can pull the electrons out of the air molecules. This flow of charge between the two charged objects can result in a spark.
78
why does balloon trick work
hair has negative charge wall has negative charge
79
how does van da graff work
touchin vandegraf allows liek charges to build up on dome and on you cuz as we now like charges repel
80
how do nuetral objects become positively charged
A neutral object can become positively charged when electrons get transferred to another object (see Figure 2). Figure 2. Positively charging a neutral object by transferring electrons to a positively charged object.
81
# not needed skip led vs halogen bulbs
Halogen bulbs, while lasting longer than incandescent bulbs, only last up to 2,000 hours. In contrast, LED bulbs can last up to 25,000 hours, and LED tubes are rated for up to 50,000 hours. LED bulbs can use as much as 80% percent less energy than halogen bulbs.
82
what is a fuse and what is its job?
A glass or ceramic canister containing a thin wire that melts if the current gets too high
83
difference between Voltage and current
: Voltage is the force that makes electrons flow. It's a difference in potential energy between two different points in a circuit. Current: Current is the rate of the flow of electrons. It's measured in amperes, which are also called amps.
84
when an electrical charge goes through a ------ in potential difference energy is transferred Energy is supplied to the charge at the --------- to 'raise' it through a potential The charge gives up this energy when it '----' through any potential drop in components elsewhere in the circuit. The formula is really simple
change power source falls energy transferred (J)= charge flow (C) * Potential difference (V)
85
what type of objects have electric fields?
electrically charged objects
86
pages in cgp workbook
43- I-V characteristics

Physics (9 decks)

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