Separate Physics - 6.2 Flashcards

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)

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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)

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22
Q

What are the two ways of joining an electrical component?

A

In series or in parallel

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23
Q

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

A

The same

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24
Q

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

A

It is shared

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25
How are step-down transformers used within the National Grid?
Step-down transformers bring the 400’000V of the National Grid down to 230V for domestic use
26
Separate Q. What causes electrical static to build up?
Friction
27
Separate Q. When certain insulating materials are ‘rubbed’ what will be scraped off one and ‘dumped’ onto the other?
Electrons
28
Separate Q. What can too much static cause?
Sparks
29
Separate Q. What do like charges do?
Repel
30
Separate Q. What do opposite charges do?
Attract
31
Separate Q. What is created around any electrically charged object?
An electric field
32
Separate Q. How does the electric field change when it is close to / far away from the charged object?
The electric field is strongest close to the charged object and further away becomes weaker
33
Separate Q. What do charged objects in an electric field ‘feel’
A force
34
Separate Q. What causes the force experienced by a charged object in an electric field?
Electric fields interact with each other (the force is linked to the strength of the electric field)
35
Separate Q. How can sparking be explained by electric fields?
* Sparks are caused when there is a high enough potential difference between a charged object and Earth * This causes a string electric field leading to ionisation allowing a current to flow
36
Separate Q. Explain the field lines
* Electric field lines go from positive to negative * They are at right angles to the surface * The closer the lines the stronger the field
37
Separate Q. Explain why the oppositely charged particles attract
* The electric fields interact * Forces act on both causing them to move closer together
38
How can the total resistance of two components in a series circuit be worked out?
The total resistance of the components in a series circuit is the sum of all of them
39
In a parallel circuit what is the potential difference across each component like?
It is the same
40
What would the total resistance of two resistors be?
Less than the resistance of the smallest individual resistor
41
What type of electricity supply is a battery?
Direct current (DC)
42
What is the equation for Rtotal?
Rtotal = R1 + R2
43
How can the total current through a parallel circuit be calculated?
It is the sum of the currents through the separate components
44
What type of electricity supply is mains?
Alternating current (AC)
45
Describe direct current supplies
Current that is always flowing in the same direction (created by a direct voltage)
46
Describe alternating current supplies
Current which constantly changes direction
47
What is a three-core cable?
Three wires (core of copper) with a brown (live wire), blue (neutral wire) and green / yellow (Earth wire)
48
What is the function of the neutral wire (blue)
Completes the circuit carrying current away (OV)
49
How can the live wire cause an electric shock?
Touching a live wire (230V) puts a large potential difference across your body (0V) which can shock / kill
50
Describe the characteristics of the UK mains supply
230V AC with a frequency of 50Hz
51
What is the function of the live wire (brown)?
Provides the alternating potential difference (230V)
52
What is the function of the Earth wire (green / yellow)?
Acts as a safety device, stopping the appliance casing from becoming live (OV)
53
Q. What equations links power, current and potential difference? Q. What equation links power, current and resistance?
Power = current x potential difference P = I V Power = current2 x resistance P = I2 R
54
What determines how much energy an appliance transfers?
How long the appliance is on for and the power of the appliance
55
Q. What equation links energy transferred, power and time? Q. What equation links energy transferred, charge flow and potential difference?
Energy transferred = power x time E = P t Energy transferred = charge flow x potential difference E = Q V
56
In the UK, how is electricity distributed?
Via the National Grid
57
How is the National Grid made as efficient as possible?
A high potential difference and a low current which, for a given power, decreases energy lost by heating (the wires / surroundings)
58
What is ‘done’ when charge flows in a circuit?
Work (done)
59
What effects of the power of a circuit?
* The potential difference and current which runs through it * The energy transferred over a given time
60
What does the National Grid comprise of?
A system of cables and transformers linking power stations to consumers
61
How are step-up transformers used within the National Grid?
Step-up transformers increase the potential difference of the National Grid to 400,000V