Brainscape's Knowledge GenomeTM

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


See full index

physics: paper 1 > electricity > Flashcards

electricity Flashcards

1
Q

relationship between current through resistor and potential difference

A

it’s directly proportional, resistance does not increase if current increased.(ohmic conductor) but this is only true when temperature is constant

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

why are resistors used?

A

to control potential difference in circuits

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

relation between current through filament lamp and potential difference

A

it is not directly proportional,
- bcs filament gets hot which increases resistance
-bcs atoms in filament vibrate more, electrons in current now collide more with the atoms,
-more energy needed to push current thru fil

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

what is resistance?

A

anything in circuit opposing flow of current

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

what is the difference between direct and alternating current?

A

dc current only flows in one direction.
-the flow of ac current is constantly changing. the mains supply for ac is at 230V and 50 Hz per second.

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

why are step up transformers used?

A

-when elec is transmitted, energy lost thru heating in cables, higher for high current.
-trans elec at high voltage reduces current for the same amount of power,
-so step up transformers are used to increase voltage, decrease current and reduce energy loss

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

explain why electricity is transmitted at a high pd

A

-to trans high power, either high pd or high current is needed. high current is less efficient as it wastes more energy as thermal from wires heating up. trans at high pd means lower current can be used which reduces energy loss meaning trans more efficient

high power trans= +pd OR +current => +energy loss,,,,, +pd= -current= - energy loss= +efficient

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

why can a large charge on an isolated object result in a spark

A

-large charge causes large pd betw obj and earth, pd can get large enough for spark to jump betw obj and an earthed conductor

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

explain with ref to elec fields how car gives man electric shock when putting hand near it

A

-car has a large static charge, pd betw car and earth is large.
-this causes strong electric field, which ionises the air particles around, so air can conduct elec,
-man is an earthed conductor, so spark jumps across gap from car to man

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

what is charge

A

measure of total current that flowed within a certain period of time

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

In a series circuit, the current is:
In a series circuit, the potential difference of the battery is:

A

-same everywhere
-shared across components

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

in a parallel circuit, every component has the same …. and shares the ….

A

-p.d.
-current

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

in a parallel circuit, loops w/ greater resistance, take a ……. …. of current

A

lower share

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

more components in a parallel circuit…

A

less total resistance

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

step up transformers increase….. and decrease ….. to minimise …..

A

-voltage / p.d.
-current
-energy loss

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

the uk mains supply is

A

230 V and 50 Hz, alternating current

16
Q

state the three wires colours and functions

A

-live, brown
provides the alternating p.d. (230V)

-blue, neutral
acts by completing the circuit and carries away current, has a p.d. of 0V

-green yellow, earth
stops appliance from becoming live in case live wire touches casing, by providing alternate pathway for current to flow

17
Q

what causes an electric shock

A

a difference in voltage causes electricity to pass from one to another
humans have a p.d. of 0V so touching live wire will cause a large current to flow through

18
Q

a sudden increase in current is called a

A

surge
could happen when you turn an appliance on or off
or because of a fault in the appliance
can damage appliance, cause fires, electric shocks

19
Q

how do fuses/ circuit breakers promote safety

A

-breaks the circuit when current gets too high
-very thin piece of wire that’s connected to live wire
-if there’s surge, huge amount of current will flow through the live wire and fuse
-fuse heats up and melts, breaks circuit

20
Q

benefit and disadvantage of fuses

A

simple and cheap
but permanently broken after a single surge, have to be replaced each time

21
Q

circuit breakers vs fuse

A

-CB doesn’t get perm. damaged
-it just gets tripped and turns off circuit
-can be reset
-more expensive than fuses

22
Q

what is double insulation

A

-appliance is covered in plastic coating
-no exposed metal parts
-plastic doesn’t conduct elec so no shock
-these appliances usually only have live & neutral wire

23
Q

what is static electricity

A

build up of charge on insulating materials

24
Q

what happens when two materials are rubbed against each other
-in terms of insulating and conducting materials

A

the electrons form one material rub off to the other material

-in conducting materials the electrons are able to move, so can just flow straight back again, thr4 no charge ever builds up (can but it is very uncommon)

-in insulating materials electrons not able to flow back so one is left with a positive static charge and other with negative static charge

25
Q

in static charges, only the ……. are being transferred

A

electrons

26
Q

what happens when an object keeps on gaining negative electrons

A

-size of the charge increases
-p.d build up betw obj and any earthed obj (any object with 0V, such as humans)
-if the p.d is big enough, electrons can jump betw the gap, causing a spark

27
Q

the field lines in a positive and negative particle

A

-goes into the negative
-comes out of positive

28
Q

what could happen when there is a strongly charged piece of metal surrounded by air

A

-air is an electrical insulator and doesn’t conduct electricity
-however, strong electrical field, like the one around metal can cause surrounding air particles to lose electrons and form positive ions, (ionisation)
-once air ionised, it can conduct electricity
this is how sparks are able to go betw objs, travelling through the air

29
Q

IV Characteristics practical
-current, p.d vary resistance, temp, switch, graph

A
  • measure the current in R using the ammeter
  • measure the p.d. across R using voltmeter
  • vary resistance of variable resistor
  • record a range of values of current and p.d.
  • ensure current low, avoid temp increase
  • switch circuit off betw/ readings
  • reverse connection of R to power supply
  • repeat measurements of I and V in negative direction
  • plot a graph of current against p.d.
30
Q

what is the error regarding eye positioning called

A

Parallax Error

31
Q

strong magnetic fields can ionise…

A

air around them, causing sparks

physics: paper 1 (5 decks)

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