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Master Combined Science - Physics (Foundation) > Combined Physics - 6.2 > Flashcards

Combined Physics - 6.2 Flashcards

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1
Q

What are the circuit symbols for a switch (open and closed), a cell and a battery?

A
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2
Q

What are the circuit symbols for a diode, resistor, variable resistor and LED?

A
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3
Q

What are the circuit symbols for a lamp, fuse and voltmeter?

A
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4
Q

What are the circuit symbols for an ammeter, thermistor and LDR?

A
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5
Q

For electrical charge to flow through a closed circuit what must be included?

A

A source of potential difference

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6
Q

What is electrical current and what determines the size of the current?

A

The flow of electrical charge, determined by the rate of flow

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7
Q

What is the equation for charge flow?

A
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8
Q

In a single closed loop, what value would the current have at any point?

A

The same value

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9
Q

What affects the current through a given component?

A

The resistance of the component and the potential difference across it

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10
Q

For a given potential difference, what happens to the current when the resistance increases?

A

The current gets smaller

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11
Q

What equation links potential difference, current and voltage?

A
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12
Q

What happens to the resistance of an ohmic conductor (such as a wire) when the current changes?

A

The resistance of ohmic conductors doesn’t change with current

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13
Q

What happens to the resistance of a diode or filament lamp when current changes?

A

Resistance increases with temperature, such as the current increases the resistance increases

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14
Q

Draw and describe an I-V graph for an ohmic resistor (e.g. a resistor at a constant temperature)

A

Current (at constant temperature) is directly proportional to potential difference

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15
Q

Draw and describe an I-V graph for a filament lamp

A

As the current increases the temperature of the filament lamp increases (so the resistance increases) meaning less current can flow per unit potential difference

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16
Q

Draw and describe an I-V graph for a diode

A

Current will only flow in one direction (there is a very high resistance in the other direction)

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17
Q

What happens to the resistance of a thermistor as temperature increases?

A

As temperature increases a thermistor’s resistance decreases

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18
Q

Where are thermistors commonly found?

A

Car engine temperature sensors / electronic thermostats (as temperature rises the resistance decreases)

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19
Q

What happens to the resistance of a LDR as light increases?

A

As light increases a LDR’s resistance decreases

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20
Q

Where are LDRs commonly found?

A

LDRs are used as automatic night lights / burglar detectors (in bright light the resistance is low)

21
Q

How are LDRs and thermistors used in sensing circuits?

A

Sensing circuits can be used to turn on / increase the power to components depending on conditions (e.g. as a room gets hotter the resistance of a thermistor decreases taking a smaller share of the potential difference from a power supply allowing a fan to get more potential difference and spin faster)

22
Q

What are the two ways of joining an electrical component?

A

In series or in parallel

23
Q

In a series circuit, what is the current like through all components?

A

The same

24
Q

How is the total potential difference distributed between the components in a series circuit?

A

It is shared

25
Q

How are step-down transformers used within the National Grid?

A

Step-down transformers bring the 400’000V of the National Grid down to 230V for domestic use

26
Q

How can the total resistance of two components in a series circuit be worked out?

A

The total resistance of the components in a series circuit is the sum of all of them

27
Q

In a parallel circuit what is the potential difference across each component like?

A

It is the same

28
Q

What would the total resistance of two resistors be?

A

Less than the resistance of the smallest individual resistor

29
Q

What type of electricity supply is a battery?

A

Direct current (DC)

30
Q

What is the equation for Rtotal?

A

Rtotal = R1 + R2

31
Q

How can the total current through a parallel circuit be calculated?

A

It is the sum of the currents through the separate components

32
Q

What type of electricity supply is mains?

A

Alternating current (AC)

33
Q

Describe direct current supplies

A

Current that is always flowing in the same direction (created by a direct voltage)

34
Q

Describe alternating current supplies

A

Current which constantly changes direction

35
Q

What is a three-core cable?

A

Three wires (core of copper) with a brown (live wire), blue (neutral wire) and green / yellow (Earth wire)

36
Q

What is the function of the neutral wire (blue)

A

Completes the circuit carrying current away (OV)

37
Q

How can the live wire cause an electric shock?

A

Touching a live wire (230V) puts a large potential difference across your body (0V) which can shock / kill

38
Q

Describe the characteristics of the UK mains supply

A

230V AC with a frequency of 50Hz

39
Q

What is the function of the live wire (brown)?

A

Provides the alternating potential difference (230V)

40
Q

What is the function of the Earth wire (green / yellow)?

A

Acts as a safety device, stopping the appliance casing from becoming live (OV)

41
Q

Q. What equations links power, current and potential difference?

Q. What equation links power, current and resistance?

A

Power = current x potential difference

P = I V

Power = current2 x resistance

P = I2 R

42
Q

What determines how much energy an appliance transfers?

A

How long the appliance is on for and the power of the appliance

43
Q

Q. What equation links energy transferred, power and time?

Q. What equation links energy transferred, charge flow and potential difference?

A

Energy transferred = power x time

E = P t

Energy transferred = charge flow x potential difference

E = Q V

44
Q

In the UK, how is electricity distributed?

A

Via the National Grid

45
Q

How is the National Grid made as efficient as possible?

A

A high potential difference and a low current which, for a given power, decreases energy lost by heating (the wires / surroundings)

46
Q

What is ‘done’ when charge flows in a circuit?

A

Work (done)

47
Q

What effects of the power of a circuit?

A
  • The potential difference and current which runs through it
  • The energy transferred over a given time
48
Q

What does the National Grid comprise of?

A

A system of cables and transformers linking power stations to consumers

49
Q

How are step-up transformers used within the National Grid?

A

Step-up transformers increase the potential difference of the National Grid to 400,000V

Master Combined Science - Physics (Foundation) (7 decks)

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