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IGCSE Edexcel Physics > 2 Electricity > Flashcards

2 Electricity Flashcards

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1
Q

Charge comes from…

A

electrons moving

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2
Q

Unit of Charge

A

Coulombs (C)

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3
Q

What is current

A

The rate of flow of charge

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4
Q

Unit of Current

A

Amperes (A) = C/s

1 Coulomb per second

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5
Q

Q =

Charge (C)

A

It

Current (A) x time (s)

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6
Q

When are the dangers of electrostatics

4 points

A
  1. Charges build up when 2 insulating materials rub against each other
  2. Electrons move from one surface to another
  3. (surfaces that gain electrons become negative, surfaces losing electrons become positive)
  4. you must ‘earth’ or ‘ground’ objects to lose charge as the electrons have a path to earth -> where they pread out
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7
Q

Why is earthing important for refuelling

A

a discharge of electrons results in a spark which can cause an explosion

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8
Q

Circuit Components

Draw an LDR

A

rectangle with 2 arrows going in

Light Dependent Resistor

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9
Q

Circuit Components

Draw a diode

A

triangle with line at pointy end

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10
Q

Circuit Components

Draw an LED

A

triangle with line at pointy end, 2 arrows pointing out of the triangle

Light emitting diode

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11
Q

Circuit Components

Draw a thermistor

A

rectangle with hockey stick

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11
Q

Circuit Components

Draw a thermistor

A

rectangle with hockey stick

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12
Q

Circuit Components

Draw a motor

A

circle with M

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13
Q

Circuit Components

Draw a fuse

A

rectangle with the wire going through it

(ONLY TIME WIRE GOES THROUGH RECTANGLE)

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14
Q

Circuit Components

Draw a variable resistor

A

reactangle with diagonal arrow going through it

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15
Q

Circuit Components

Draw a transformer

A

on either side of the wire (not going through the wire), 4 bumpy edges

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16
Q

Describe an experiment to investigate charging by friction

A
  1. rub both ends of a polythene rod with a cloth
  2. suspend the rod without touching the end, from a strand using a cradle and nylon thread
  3. take a rod of different insulating material and rub it with another cloth of the same material
  4. record any observations
  5. repeat with different materials and compare
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17
Q

Give the variables from the experiment

A

Independent - different rods material
Dependent - charge on rod
Controlled - 1. time spent rubbing rod
2. using same type of cloth
3. using same length of rod

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18
Q

Results from experiment

A
  1. When 2 insulating materials rub together - electrons pass from one insulator to another insulator
  2. polythene rod beomes negatively charged after being rubbed with cloth -> electrons move from cloth to rod
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19
Q

Current flows from…

A

positive -> negative

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20
Q

current along a wire with no junctions is …

A

constant

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21
Q

current at a junction is…

A

conserved
this means -> total current in = total current out

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22
Q

Unit of voltage (potential difference)

A

volts = j/c

joules/coumlob

23
Q

ELECTRICITY

A
24
Q

know the units for :
current =
charge =
resistance =
time =
potential difference =
power =

A

current = Ampere (A)
charge = coulomb (C)
resistance = ohm (Ω)
time = second (s)
potential difference = volt (V)
power = watt (W)

25
Q

Explain how fuses protects the device or user in domestic appliances

A

Stop the flow of current by melting if the current is too high. So protecting sensitive components and people because if the components function at too higher temperature it can cause a fire.

26
Q

Explain how circuit breakers protects the device or user in domestic appliances

A

breakers again break the circuit if current is too high.

27
Q

Explain how insulation and double insulation protects the device or user in domestic appliances

A

prevent people from touching exposed wires and getting shocks.

28
Q

Explain how earthing protects the device or user in domestic appliances

A

provides a low resistance path to the earth so if some one does come into contact with a current instead of flowing through them to the earth giving them a shock it flows through the earthing wire.

29
Q

why a current in a resistor results in the electrical transfer of energy and an increase in temperature, and how this can be used in a variety of domestic contexts

A

Resistance causes transfer of electrical energy to heat energy. Some components are designed to have a high resistance to make sure this happens, for example electrical heaters that have lots of resistors to ensure a high resistance so a lot of heat is produced.

30
Q

Power =
P =
(watts)

A

current x voltage
I x V
(A) x (V)

31
Q

what is a volt equivalent to

A

Joule/coulomb
J/C

32
Q

how to pick which fuse is correct when given

A

current of fuse should be slightly higher than current in circuit - so if circuit heats up normally and fuse keeps breaking even though current isn’t too high - then fuse current is too low
fuse amps (3A, 5A, 13A)

33
Q

Energy (J) =

A

potential difference (V) x current (A) x Time (s)
I x V x t

34
Q

Alternating current:
describe the motion of the current

A

current constantly changes direction

35
Q

Direct current:
describe the motion of the current

A

current flows in only one direction

36
Q

is mains eletricity AC or DC supply?
what voltage, frequency and current?

A

AC
230V
50Hz

37
Q

do batteries and solar cells supply AC or DC electricity?
how much would a typical battery supply

A

DC
1.5 V

38
Q

why a series or parallel circuit is more appropriate for particular applications, including domestic lighting

A

Advantages of parallel circuits:

Components (e.g. bulbs) may be switched on/off independently.
If one component breaks, current can still flow through the other parts of the circuit.
Bulbs maintain a similar brightness.

Advantages of series circuits:

Fewer wires, cheaper and easier to assemble.
Uses less power

39
Q

as voltage increases in a circuit, current also________

A

increases

40
Q

the more components in a circuit, the _______ the current

A

lower

41
Q

describe graph of wire, filament lamp, diode as graph shows how current varies with voltage
(resistance changed using variable resistor)

A

wire - directly proportionate
filament lamp - s curve
diode - horizontal line and sudden steep gradient

42
Q

changing resistance in a circuit will _________ the current

A

decrease as V = IR

43
Q

describe how resistance changes in an LDR

A

as light increases, resistance decreases

44
Q

describe how resistance changes in a thermistor

A

as temperature increases, resistance decreases

45
Q

how to check if there is current in a circuit

A

add lamp, if current is flowing, lamp will light up

46
Q

current is the ….

A

rate of flow of charge

47
Q

so I =

A

Q/t

48
Q

Q =
Charge (C) =

A

I x t

49
Q

electric current in solid metallic conductors is a flow of ….

A

negatively charged electrons - free to flow in metals so carry charge - negative electrons attracted to positive charges

50
Q

why current is conserved at a junction in a circuit

A

At a junction current ‘splits’ to take both paths.

It comes back together when the paths meet again.

I1 = I2 + I3 +I4

51
Q

how is voltage and current, resistance split in a series circuit?

A

voltage - split between components
current -same for each component
resistance - split between components

52
Q

how is voltage and current split in a parallel circuit?

A

voltage - same for each component
current - split between branches

53
Q

voltage =

A

energy transferred / charge
J/C

54
Q

energy transferred (J) =
E =

A

charge (C) x voltage (V)
QV

55
Q

conducting materials

A

Copper
Aluminium
Gold
Silver

56
Q

Insulating Materials:

A

Glass
Air
Plastic
Rubber
Wood

IGCSE Edexcel Physics (10 decks)

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