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GCSE - Physics > P4 - electric circuits > Flashcards

P4 - electric circuits Flashcards

1
Q

how do you charge insulators

A

rub them with another insulator like a dry cloth

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2
Q

why does rubbing an insulator charge it

A

electrons are transferred from one of the materials to the other

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3
Q

what happens when two like charges are put near eachother

A

they repel

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4
Q

what happens when you put two unlike charges near to eachother

A

they attract

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5
Q

what is a non contact force

A

the force between two charged objects

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6
Q

what happens when a field is too strong and why

A

sparking happens because some electrons are pulled out of air molecules by the force of the field

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7
Q

what happens when you rub a polythene rod with a dry cloth (in terms of electrons)

A

electrons transfer from cloth to rod
rod becomes negatively charged

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8
Q

what happens when you rub a perspex rod with a dry cloth (in terms of electron transfer)

A

electrons transfer from rod to cloth
rod becomes positively charged

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9
Q

what is a cell used for

A

pushing electrons around a complete circuit

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10
Q

what does a switch do

A

enables the current in a circuit to be switched on or off

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11
Q

what does a bulb (indicator) do

A

emit light as a signal when a current passes through it

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12
Q

what does a diode do

A

allow current through in one direction only

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13
Q

what does a light emitting diode (LED) do

A

emit light when a current passes through it

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14
Q

what does an ammeter do

A

measure electric current

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15
Q

what does a fixed resistor do

A

limit current in a circuit

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16
Q

what does a variable resistor do

A

allow current to be varied

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17
Q

what does a fuse do

A

melt and ‘break’ the circuit if the current through it is higher than a certain amount

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18
Q

what does a heater do

A

transfer energy from an electric current to heat surroundings

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19
Q

what does a voltmeter do

A

measure potential difference (voltage)

20
Q

what is the size of an electric current

A

the rate of flow of electric charge
flow of charge per second

21
Q

what is the current at any point in a single closed loop

A

the same as the current at any other point

22
Q

what is the equation for charge flow

A

charge flow (Q) = current (I) x time taken (t)

23
Q

what is the current at any point in a series circuit

A

the same as any other point

24
Q

what is the equation for potential difference across a component

A

potential difference across a component = energy transferred / charge

25
Q

what is the equation for resistance

A

resistance = potential difference / current

26
Q

what is ohms law

A

the current through a resistor at constant temperature is directly proportional to the potential difference across the resistor

27
Q

what does reversing the potential difference across a resistor do

A

reverse the current through it

28
Q

in a filament lamp, is current directly proportional to the PD?

A

no

29
Q

what happens in a filament lamp as the temperature increases

A

the resistance increases

30
Q

why does the resistance increase as temperature increases in a filament lamp

A

the atoms in the metal filament vibrate more as temperature increases
so they resist passage of electrons through filament more

31
Q

what happens to the resistance if you reverse the potential difference in a filament lamp

A

it’s the same

32
Q

in a diode, is current directly proportional to PD?

A

no, the resistance changes as the current changes

33
Q

what happens when you change a diodes direction

A

reverse direction resistance is a lot higher than forward resistance

34
Q

what is a thermistor

A

a temperature dependent resistor

35
Q

what happens to a thermistors resistance if it’s temperature increases

A

it decreases

36
Q

what happens to an LDRs resistance if light intensity increases

A

it decreases

37
Q

what is the current in each component in a series circuit

A

the same as every component

38
Q

in a series circuit, what happens to the potential difference

A

it is shared between the components

39
Q

what is the total PD of cells in series the sum of

A

the potential difference of each cell

40
Q

what is the equation for total resistance in series

A

total resistance = R1 + R2

41
Q

what happens when you add more resistors in series

A

the total resistance increases
current through resistors is reduced
PD is unchanged

42
Q

what is the rule about current for components in parallel

A

total current through whole circuit is sum of currents through separate branches

43
Q

what is the rule about PD for components in parallel

A

PD across each component is the same

44
Q

in a parallel circuit, what happens to the current if the resistance increases

A

the current decreases

45
Q

what is the equation for current through a component

A

current = PD/component resistance

46
Q

what is the rule for resistors in parallel

A

total resistance of two (or more) components in parallel is less than resistance of the resistor with the least resistance

47
Q

why does adding for resistors in parallel decrease the total resistance

A

the total current through the resistors in increased
PD across them is unchanged

GCSE - Physics (7 decks)

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