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Physics > P2 > Flashcards

P2 Flashcards

1
Q

Voltmeter

A

measures the potential difference across a component

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2
Q

Ammeter

A

measures current

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3
Q

Battery / Cell

A

Provides energy to the electrons in a circuit

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4
Q

Switch

A

Connects / Disconnects the circuit

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5
Q

Resistor

A

Resists current

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6
Q

Diode

A

Keeps current flowing in one direction

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7
Q

Thermistor

A
  • Resistance decreases as temperature increases
  • When temperature increases, additional energy can be used to increase the kinetic energy of electrons (current)
  • More current = less resistance
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8
Q

Light Dependant Resistor

A

Resistance decreases as light increases
- When light increases, additional energy can be used to increase the kinetic energy of electrons (current)
- More current = less resistance

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9
Q

Voltage

A

Amount of energy supplied to each Colomb

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10
Q

Potential Difference

A
  • The difference in energy per charge between 2 points in a circuit
  • Shows how much energy is supplied to a component
  • YOU ALWAYS CALCULATE THIS
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11
Q

Current Calculation?

A

Current = Charge / time

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12
Q

Energy Calculation?

A

Energy = Charge x Potential Difference

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13
Q

Current in a series circuit…

A

Always stays the same

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14
Q

Current in a parallel circuit…

A

Splits between the pathways

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15
Q

Potential Difference in a series circuit…

A

Is shared amongst the components

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16
Q

Voltage in a parallel circuit…

A

Stays the same

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17
Q

More resistors in series…

A

= more resistance

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18
Q

More resistors in parallel…

A

= more pathways = more current = less resistance

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19
Q

Ohms law

A
  • Current flowing through a resistor is directly proportional to the potential difference
  • Current across a resistor is inversely proportional to the resistance
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20
Q

What is the only condition for ohms law?

A

If Temperature is Constant

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21
Q

Resistance in Parallel circuit?

A
  • Total resistance is always less than the lowest resistance in the circuit
  • Rt = 1 + 1
    R1 R2
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22
Q

What is the gradient on a V-I graph for a resistor?

A

Resistance

23
Q

If a component obeys ohms law what WILL be constant?

A

Resistance

24
Q

Does a filament Bulb follow Ohm’s law?

A
  • Up to a certain point where the line starts to curve
  • This is because after a while, temperature increases which leads to more resistance leading to less current
25
Q

Why does temperature affect resistance?

A
  • Inside wires are delocalised electrons that carry a charge
  • Increase in temperature = more kinetic energy
  • more electrons collide with cations
  • Which delays current, slowing is down
  • Which is resistance
26
Q

Do diodes follow Ohms’s law?

A
  • No, resistance isn’t constant
  • A Diode has low resistance in one direction and high resistance in the other direction
    (The current through a diode flows in one direction only. The diode
    has a very high resistance in the reverse direction.)
27
Q

Why are people rarely electrocuted by appliances?

A
  • Use plastic around wires
  • Plastic is an insulator; cant carry electricity
  • Fuse
28
Q

What is double insulation?

A

An appliance with a plastic case is double insulated

29
Q

What are wires made from and why?

A
  • Copper
  • Bends easily
  • Group 3: for every ion, there are 3 delocalised electrons which can carry more overall energy
  • Light
30
Q

What are pins made from and why?

A
  • Brass
  • Not very reactive (doesn’t rust)
  • Doesn’t bend
  • Good conductor
31
Q

Why is the diameter of a wire important?

A
  • Wider diameter = more current = less resistance
  • May overheat
32
Q

Why do we use Plastic to cover the wires?

A
  • Good insulators
  • colours make it easy to label wires
33
Q

What are the wires and their colours?

A

live wire – brown
neutral wire – blue
earth wire – green and yellow stripes.

34
Q

What does the live wire do?

A

Carries the potential difference (230V) from the supply

35
Q

What does the earth wire do?

A

An earthing/grounding system connects certain parts of an electric system to the ground to absorb the current

36
Q

What is the Neutral wire for?

A
  • Completes the circuit
  • If it gains voltage the earth wire will be used
  • Voltage should always be 0
37
Q

Fuse

A

A component with a wire running through it, which is melted when there is too much current

38
Q

Why do you want your fuse to be more than the current that you have?

A

Anything more than the current will blow the fuse

39
Q

Where is the fuse in the circuit?

A

Between the live wire and the appliance so that if a fuse blows, the appliance is cut off from the live wire supply

40
Q

What are circuit breakers

A

If they notice an increase in current to the fuse a switch will trip (open), stopping the flow of current

41
Q

Why are circuit breakers better than fuses?

A
  • Notice a very slight difference in current, whereas fuses only notice a 3 Amp difference
  • Can be reset easily, unlike fuses which need to be replaced
42
Q

Power equations?

A

Power = current x potential difference
Power = Resistance x current^2

43
Q

What is power?

A

Amount of energy transferred / second to the electrons

44
Q

Genortaor?

A

Generates electricity which is transported around the country

45
Q

Pylon?

A

Supports the elctric cables

46
Q

What holds the wires together

A

Cable grip

47
Q

Cables

A

Transport electricity around the country

48
Q

Transformer

A

Increases/decreases voltage at particular stages in the national grid

49
Q

Calculations for the amount of energy transferred to appliances?

A

Energy = Power x Time
Energy = Charge x Potential Difference

50
Q

Why is the national grid efficient?

A
  • Uses step-up transformers to increase the potential difference which makes current decrease to keep power constant: which limits the collisions between the electrons and cations which creates wasted thermal energy (high current = cables get hot)
  • Uses step-down transformers before it reaches your home to decrease the potential difference so it doesn’t kill you
  • It’s efficient since it limits energy wasted
51
Q

Pros and Cons of Underground Cables?

A

P Doesnt affect landscape
P not affected by weather
C Expensive
C Difficult to put
C High Maintenence
C Cause damage if breaks

52
Q

Pros and Cons of Overhead Cables?

A

P Higher Voltage
P Easier to repair
P Cheaper
C Affected by weather
C Heat dissaptaion

53
Q

Alternating Current

A

Current is continuously changing directions

54
Q

Static Electricity

A

Physics (4 decks)

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