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Physics paper 2 > SP10 > Flashcards

SP10 Flashcards

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1
Q

describe the mass and relative charge of a proton, neutron, electron

A

proton
mass - 1
charge - +1

neutron
mass - 1
charge - 0

electron
mass - 1/2000 or negligible
charge - -1

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2
Q

what direction does conventional current flow through in a circuit

A
  • from the negative end of cell to the positive end of the cell
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3
Q

what direction does electrons flow

A

positive to negative terminal

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4
Q

what is a series circuit

A

a circuit where there is only one route where current can flow

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5
Q

what are the differences between series and parallel circuits

A
  • parallel has multiple routes current can flow through and series has one direction
  • in a series circuit, if a switch is switched off all the bulb go off due to one route of current
    in a parallel circuit due to multiple routes, bulbs can be switched off individually
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6
Q

what is a parallel circuit

A

a circuit where there a junctions allowing for current to flow through different route

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7
Q

how is a voltmeter connected in a circuit

A

it is connected parallel to a component

    ---BULB---
    I                I
    I\_\_\_\_v\_\_\_\_I
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8
Q

what do voltmeters measure

A
  • voltage / potential difference , in volts
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9
Q

what is meant by potential difference ( voltage)

A

the amount of energy per unit charge to move electrons from one point to the next

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10
Q

what is the unit of measure for voltage

A

volts
volt is a joule per coulomb

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11
Q

how is an ammeter connected in a circuit

A

it is connected in series with a component

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12
Q

what does an ammeter measure

A

current , amps

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13
Q

what is electrical current in a circuit
( what ammeters measure)

A

the flow of charge

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14
Q

what is the current in metals

A

the flow of electrons

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15
Q

what happens to current at a junction

A

current is conserved at a junction in a circuit

the total current flowing into a junction is equal to total current flowing out

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16
Q

what is resistance

A

the difficulty for current to flow

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17
Q

explain how changing resistance changes the current

A
  • due to more difficulty for current to flow through
  • higher potential difference is needed
  • more energy in electrons to allow them to move
  • therefore, more energy in the current
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18
Q

how can the resistance of a circuit change

A

using a variable resistor
(a resistor which electrical resistance values can be adjusted)

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19
Q

why is it that if 2 resistors are in series, the net resistance is increases

A
  • the pathway becomes harder for current to flow through
  • the potential difference from cells are not shared equally between the resistor
  • there will be greater Pd across resistors with higher resistance
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20
Q

explain why if 2 resistors are in parallel, the net resistance decreases

A
  • the resistance decreases in a parallels circuit with 2 resistors
  • as there are more pathway for the current to flow in
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21
Q

Explain how current varies with potential difference for filament lamps, relate to resistance

A
  • pd across a filament lamp causes current to flow through it
  • more pd causes more current, cause it to get hot
  • the hotter the bulb gets the more resistance increases
  • so the pd will change but the current wont, so the bulb doesn’t break
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22
Q

what is a diode

A

it is a component which causes the current to flow in one way

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23
Q

Explain how current varies with diode for filament lamps, relate to resistance

A

there is a low resistance when pd is flowing in one direction
there is a high resistance when the pd is flowing in the wrong direction

this means that the current can only flow in one direction

24
Q

Explain how current varies with potential difference for fixed resistors, relate to resistance

A

the resistance stays the same
because potential difference and current being directly proportional

25
Q

Describe how the resistance of a light-dependent resistor (LDR) varies with light intensity

A

high resistance in the dark
low resistance in light

26
Q

Describe how the resistance of a thermistor varies with change of temperature

A

high resistance in low temperatures
low resistance in high temperatures

27
Q

how the design and use of circuits can be used to explore the variation of resistance in a filament lamp

A

Connected to DC of 2, 4, 6, …
-Connect the filament lamp to Ammeter in series and Voltmeter in parallel
-Measure the current for each voltage
-Plot a graph to show relationship between the pd and current
-Non-linear shows Resistance varies

28
Q

how the design and use of circuits can be used to explore the variation of resistance in a diode

A

-Connected to DC of 1, 1.5, 2, 4, 6, …, 10, 12V –Connect to an Ammeter in series and Voltmeter in parallel
-Measure the current for each voltage
-Switch the diode the other way round to record current for -1, -1.5, -2, -4V
- Plot graph for the positive and negative potential differences to show the relationship

29
Q

how the design and use of circuits can be used to explore the variation of resistance in a thermistor

A
  • Constant voltage of 12V
  • Connect to an Ammeter
  • Place in ice water with thermometer
  • Measure current at 0 degrees.
  • Add hot water and stir, measuring current at 10, 20, …, 60 degrees
  • Calculate the resistance
  • Plot a graph of resistance against temperature
30
Q

how the design and use of circuits can be used to explore the variation of resistance in a LDR

A
  • Constant voltage of 12V
  • Connect to ammeter
  • Shine lamp immediately onto LDR and measure current
  • Move the lamp ~10cm away and measure current o Keep doing this until 50cm
  • Calculate resistance at each light intensity
  • Plot graph of resistance against light intensity
31
Q

what happens when there is electrical current in a resistor

A

there is a heat transfer which heat up the resistor

32
Q

what happens when electrical current works against electrical current

A
  • energy is transferred as electricity work is done against resistance
  • energy is transferred by heading and the resistor become warm
    ( can be good in heaters and kettles)
33
Q

Explain the energy transfer which heats a resistor is sure to the collisions between electrons and the ions in the lattice

A
  • as electrons flow through a lattice, the ion collide with each other
  • the more collisions they make with the ions makes it harder for current to pass so the higher the resistance
  • when electrons collide with the ions, they transfer heat energy to them
34
Q

Explain ways of reducing unwanted energy transfer in wires

A
  • use metals with low resistance, such as copper, in wires
  • or thicker wires to reduce resistance
  • or cooling metals
  • so ions are not vibrating as much so that thermal energy is reduced
35
Q

Describe the advantages and disadvantages of the heating effect of an electric current

A

+ useful in kettles
+ useful in an electric heater
- computer, wires and plugs and heat is transferred to not useful energy transfers such as heat

35
Q

what is power

A

the energy transferred per second
measures in watts (w)

36
Q

Explain how the power transfer in any circuit device is related to the potential difference across it and the current in it

A

the electrical power is directly proportional to the potential difference across and current flowing through it.
power = pd x current

37
Q

what is the main electricity

A

when a applaince needs a large amount of energy so uses it from a power station, and transfers it to out homes through the national grid

38
Q

what is the national grid

A

a network of cables and wires that electricity is carried in from the power stations to out homes

39
Q

what current does the main electricity bring

A

alternating current

39
Q

how does out home use the mains electricity

A
  • it is taken from the power stations
  • through the national grid into our homes
  • and supply electricity to appliances such as the motor in the washing machine
40
Q

what is alternating current

A

where the current keeps on changing direction due to electrons mocving in one direction then the other direction

41
Q

Explain the difference between direct and alternating voltage

A

dc - the charge stays the same
eectrons flow in the same direction

ac - the charge changes constantly
- variying voltage
- electrons flow back wards and forwards, swapping constantly

42
Q

Describe direct current

A

movement of charge in one direction only
cells and batteries supply direct current

43
Q

Describe alternating current

A

the movement of charge changes direction

44
Q

what is the frequency and voltage of the main electricity ( alternating current)

A

frequency - 50Hz
voltage - 230V

45
Q

Explain the function of the neutral mains input wires

A

is the return path to the power station
carries the electricity back to the mains
completes the circuit
the voltage of the wire is 0V

45
Q

what are the three wires in a plug ( which is connected to the mains electricity)

A
  • earth wire (green and yellow)
  • blue ( neutral wire)
  • brown wire ( live wire)
46
Q

Explain the function of the live wire

A

connects appliance to the generator at the power station
the voltage of the wire is 230V

47
Q

Explain the main function of the earth wire

A
  • ensures safety
  • connects the metal part of the appliance to a large metal spike underground
  • so the current would flow into the ground if something went wrong
  • it is at 0 V
48
Q

what is the function of a fuse

A
  • a safety mechanism in the plug
  • when the current passes through the live wire too much
  • the live wire gets hot
  • melts the wire in the fuse
  • preventing the current from flowing
  • in cases too much current is flowing
49
Q

what is the function of a circuit breaker

A

they can detect when the current changes in a wire, so can safely switch off the supply

50
Q

Explain why switches and fuses should be connected in the live wire of a domestic circuit

A
  • for safety
51
Q

Recall the potential differences between the live, neutral and earth mains wires

A

live - 0 V
neutral - 230 V
earth - 0 V

52
Q

Explain the dangers of providing any connection between the live wire and earth

A

causes a very low resistance
- allows for lots of current to flow to the earth wire
- which heats up the wire
- can cause afire which could blow the fuse and cut off the mains electricity supply

53
Q

what is power rating and an example

A

Power Rating – the power of the appliance when in use
- Greater power rating, greater energy consumption per second
- So uses more energy in a given time

a kettle transfers 3000kW from the main electric supple to a store do thermal energy in water

Physics paper 2 (6 decks)

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