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Physics > Circuits > Flashcards

Circuits Flashcards

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1
Q

describe how the lamp works

A

electrical current heats the filament lamp in a bulb so that it gives out light

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2
Q

describe role of a fixed resistor

A

restricts or limits flow of electrical charge

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3
Q

explain role of variable resistor and what it is used in

A

modify the amount of resistance in circuit

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4
Q

describe resistance in a thermistor

what use thermistors?

A

depends on its temperature - as temp increases resistance decreases
thermostats and heat activated fire alarms

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5
Q

describe resistance in LDR

what contains LDR?

A

resistance depends on light intensity, at low light ldr has high resistance. as light intensity increases, resistance decreases
can be used in automatic lights

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6
Q

explain what a diode does and why its used

A

allows current to flow only one direction, used to convert alternating current in other direction

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7
Q

what is a cell?

A

store of chemical energy

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8
Q

what is a battery?

A

2 or more cells in series

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8
Q

what is the formula for current (not ohms law one)?

A

charge / time

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8
Q

state the formula for charge

A

current x time

I x t

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8
Q

state the formula for potential difference

A

current x resistance

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8
Q

state the formula for resistance

A

pd / current

v / I

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9
Q

state the formula for power transferred

A

I x v

current x pd

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10
Q

state the formula for power absorbed

A

I2 x R

current squared x resistance

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11
Q

what causes resistance?

A

when electrons collide with ions in the conductor

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12
Q

how must voltage be measured?

A

in parallel

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13
Q

what scientific term describes the electrons in a metal when a current flows through it?

A

delocalised

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14
Q

how do you calculate voltage?

A

current x resistance

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15
Q

what does ohms law state?

A

electric current is proportional to voltage and inversely proportional to resistance

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16
Q

how do you find total resistance of a circuit in series?

A

add all resistors together

R1 + R2 + R3

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17
Q

what are the two types of current

A

direct and alternating current

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18
Q

what is direct current

A

the flow of electrons is consistently in one direction around the circuit

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19
Q

what is alternate current

A

the direction of electron flow continually reverses

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20
Q

what is electrical current

A

a flow of electrons / flow of electrical charge

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21
Q

what is charge

A

amount of electricity travelling in a circuit

22
Q

how do you measure pd across component

A

voltmeter must be placed in parallel with the component order to measure difference in energy from one side of component to the other

23
Q

how do you measure current through component

A

ammeter must be placed in series with component

24
Q

what is potential difference

A

the driving force that pushes the charge around

and a measure of how much energy is transferred between 2 points in a circuit

25
Q

explain the role of a fuse in a circuit

A

they break/melt if too much current flows through the circuit

26
Q

what do ammeters measure

A

current

27
Q

in series, the potential difference of the battery is…

A

shared across all of the components

28
Q

in a series circuit the current is…

A

the same everywhere in the circuit

29
Q

how do you work out total resistance in a series circuit

A

add all resistors together

30
Q

what happens if one bulb in a series circuit breaks?

A

current won’t beable to flow around the circuit so all other bulbs will go out

31
Q

in parallel circuits total current supplied is…

A

split between all the components on different loops

32
Q

in parallel circuits the potential difference is…

A

the same across each loop

33
Q

why will adding a resistor to a parallel circuit which already has one resistor decrease the overall resistance?

A

adding another resistor will also add another loop introducing another possible pathway for current to flow

34
Q

how do you calculate voltage drop

A

current x resistance

35
Q

state the formula for finding total resistance of a parallel circuit

A

1/R1 + 1/R2 + 1/R3 + 1/R4

36
Q

once you have added the fractions when working out total resistance of a parallel circuit, what do you need to remember to do?

A

flip the fraction so you can divide

37
Q

using ohms law how do you work out current in a circuit?

A

potential difference / resistance

38
Q

a battery is connected in series with a 4 ohms resistor, 5 ohms resistor and a 6 ohms resistor. a current of 0.6A flows through the circuit. calculate the potential difference of the battery

A

4+5+6=15

15 x 0.6 = 9V

39
Q

a series circuit has two resistors of 2 ohms and 3 ohms with a 20V cell. calculate the current passing through the circuit

A

2+3=5

20 / 5 = 4A

40
Q

why does an ohmic conductor graph have a straight line?

A

the current through an ohmic conductor (at constant temperature) is directly proportional to potential difference so you get a straight line

41
Q

why does a filament graph have a curved line?

A

as current increases, the resistance increases. the temperature increases as the current flows

42
Q

a diode has a very high resistance in what direction?

A

reverse

43
Q

what is the 2 formulas for energy transferred!

A

power x time OR charge x pd

44
Q

what is resistance?

A

anything that slows the flow down

45
Q

what I-V characteristic does a linear component have?

give an example of a linear component

A

straight line

fixed resistor

46
Q

what I-V characteristics does a non linear component have?

give an example of a non linear component

A

curved line

filament lamp

47
Q

what does I-V characteristics refer to?

A

a graph which shows how the current flowing through a component changes as the potential difference across it is increased

48
Q

state another formula for potential difference (not ohms law)

A

energy / charge

49
Q

give another formula for potential difference (not ohms law)

A

energy / charge

50
Q

what is current?

A

a measure of the flow of electrons around a circuit

51
Q

how does current split between the loops in parallel circuits

A

loops that have greater resistance receive a lower share of circuits current which is why we get more current flowing in loops with smaller resistance

52
Q

all components in parallel have … potential difference

A

the same

53
Q

in series, components with a … resistance will always have a … share of voltage

A

greater

54
Q

what is conventional current?

A

assumes current flows out of the positive terminal through the circuit and into the negative terminal

55
Q

which terminal do electrons actually flow out of and why

A

the negative terminal, because electrons are negatively charged they flow around the circuit from the negative terminal to the positive terminal.

56
Q

in terms of battery/cell diagram, which line is the negative terminal and which line is the positive terminal?

A

negative - shorter line

positive - longer line

57
Q

what are step up transformers and what are the benefits

A

increases voltage, decreases current

increases efficiency, reduces heat loss

58
Q

what are step down transformers and why are they useful?

A

decrease voltage, increase current

makes safer for houses

Physics (2 decks)

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