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Physics > Electricity > Flashcards

Electricity Flashcards

1
Q

Labelling circuit symbols

A

Cell
Battery
Switch open
Switch closed
Filament lamp
Ammeter
Voltmeter
Resistor
Variable resistor
Fuse
Thermistor
Diode
LED
LDR

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2
Q

What component in a circuit need to always be in parallel and what needs to always be in series

A

Ammeter - series
Voltmeter - parallel

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3
Q

What is curent and what is the rate of flow or current?

A

Current- flow of negative electrons

Rate of flow / size of current = Charge

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4
Q

In what direction does current flow

A

Negative to positive

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5
Q

What is the relationship between a component’s current and reistance

A

The greater the resistance, the smaller the current (with equal potential difference)

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6
Q

How are ohmic conductors different to regular components

A

In usual components the resistance can change with the current.
Resistance does not change with the current in ohmic conductors

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7
Q

What is potential difference and how does it work in a circuit

A

The force driving the flow of electrons, it us provided by a cell or battery

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8
Q

What happens in an ohmic conductor at constant temperature

A

The current is directly proportional to the potential difference

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9
Q

What will an ohmic conductor look like on an I-V graph

A

Straight line (linear)

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10
Q

What is an example of an ohmic conductor

A

Fixed resistor

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11
Q

Why does a filament lamp NOT have a straight line on an I-V graph and what line does it have instead?

A

It has a curved line.

Filament lamps produce alot of thermal energy, which increases it’s resistance so less power can flow with the same amount of pd.

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12
Q

Why does a diode only have results on one side of the I-V graph and how does it do this?

A

A diode only lets current pass through it in one direction. The current can only flow one way as one direction has very low resistance, and the other very high.

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13
Q

How is potential difference measured in series

A

By adding all the PDs in the circuit

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14
Q

How is current measured in series

A

They are all equal

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15
Q

How is resistance measured in series

A

By adding the resistances in the circuit

Resistors have to share pd so the pd in each resistor is lower.

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16
Q

How is potential difference measured in parallel

A

They are all equal

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17
Q

How is current measured in parallel

A

They are added together

18
Q

How is resistance measured in parallel

A

If you have 2 resistors in parallel, the overall resistance is less than the resistance of the smallest resistor

19
Q

What is an LDR

A

Light dependent resistor

A resistor that is dependent on the intensity of light.

20
Q

What is a Thermistor

A

Resistors that depend on the temperature.

A thermistors resistance decreases as the temperature increases.

21
Q

What happens in hot and cool conditions for a thermistor

A

Hot - Resistance drops

Cool - Ressistance rises

22
Q

Where can thermistors be used (2)

A

Thermostats

Car engines

23
Q

Define AC and DC

A

Alternating current - current that changes direction (positive and negative keep alternating)

Direct current - current that only flows in one direction

24
Q

What is the meausre of pd in the UK mains supply and what type of current is it?

A

Alternating current at 230v

25
Q

What is the frequency of UK mains supply

A

50Hz

26
Q

What are the three core cables made out of

A

Copper inside (conductor)

Plastic coating outside (insulator)

27
Q

What wire is brown?
How many volts does it carry?

A

Live wire
230v

28
Q

What wire is blue?
How many volts does it carry?

A

Neutral wire
0v

29
Q

What wire is yellow and green?
How many volts does it carry?

A

Earth wire
0v
For protection against the live wire

30
Q

How is the loss of thermal energy in the National Grid’s wires prevented

A

If a high current is is used, the wires would heat up and alot of thermal energy would be lost, instead they increase and decrease the potential difference with step up and down transformers

31
Q

What is the potential difference after current flows through the step up transformer

A

400,000 V

32
Q

Describe the process of current flowing through the National Grid

A

Power Station –>
Step up transformer –>
Pylons and electricity cables –>
Step down transformer –>
Consumers –>

33
Q

What is static charge? Where is it often found?

A

Electric charge that doesn’t move can often be found on electrical insulators where charge cannot flow

34
Q

What happens when isolated materials are rubbed together?

A

Friction will cause negatively charged electrons to be scraped off one another.

35
Q

How are positive electrostatic charges produced?

A

By having negatively charged electrons move away from the electrical insulator. (Positive charges cannot move)

36
Q

How does sparking happen? Refer to electric charge and potential difference

A

As electric charge builds up on an object the pd between the object and the earth will increase. If it gets large enough electrons can jump across the gaps between the charged object and the earth at 0V to create a spark

37
Q

What is electrostatic attraction/repulsion?

A

When two charged objects either attract or repel each other and can cause objects to move due to the force

38
Q

What is an electrical field and how are they shown

A

An electrical field is created around any electrically charged object.

They can be showed using field lines

39
Q

What must be remembered when drawing field lines for electric fields

A

The lines must be at a right angle to the object’s surface

They always point away from positive charge and towards negative charge

40
Q

What happens when an object gets into another object’s electrical field?

A

It feels a force and may be repelled or attracted to it, may depend on how strong the attraction or how close the object is

41
Q

What is ionisation

A

Air is an insulator but an electric field can cause electrons in Air particles to be removed (ionisation). This means the Air can now carry charge as it’s lost electrons so charge can flow through, creating a spark

Physics (4 decks)

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