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Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

How can you make something charged

A

By the movement of electrons

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2
Q

What does friction do

A

It makes an insulating material lose or gain electrons

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3
Q

Why do hairs stand on end with a van de graaf

A

U touch the van de graaf and become charged so the hairs stand on ends because each hair has the same charge and repel

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4
Q

What are conducters

A

They have free flowing electrons

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5
Q

Like charges

A

Repel

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6
Q

Unlike charges

A

Attract

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7
Q

What is current

A

A flow of charged particles

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8
Q

What is the battery for

A

It acts as a push for the electrons, the higher the voltage the quicker the electrons are pushed, making the bulb brighter

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9
Q

Current in series

A

It is the same through each component

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10
Q

Current in parallel

A

The current is split at each branch before adding back up at the end , the same it was before splitting

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11
Q

Potential difference in series

A

The voltage is split between components but add up to the voltage of the cell or battery , they are dimmer

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12
Q

If the voltage is small or shared

A

The lights will be dimmer

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13
Q

Potential difference in parallel

A

The voltage is the same on each branch as the cell or battery

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15
Q

Resistance in series

A

The total resistance is the resistors added together because the current is the same throughout and each electron has to pass through each resistor

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16
Q

Resistance in parallel

A

The branch with the highest resistance will have the least current flowing through it. The total resistance is reduced and is less than the value of the smallest resistor

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17
Q

What is resistance measured in

A

Ohms

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18
Q

What is charge measured in

A

Coulombs

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19
Q

How does resistance happen

A

It is when the electrons collide with ions in the wire

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20
Q

What increases resistance

A

Tenperature- there is more kinetic energy for the ions therefore they vibrate and the electrons are more likely to bump into
Increasing length of wire
Making wire thinner

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21
Q

IV Resistor graph

A

It is a straight line graph this shows that the current is directionally proportional to the voltage provided it is at a constant temperature

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22
Q

IV graph filament lamp

A

As the bulb gets hotter the resistance increases therefore the rate of the increase of the current will decrease

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23
Q

IV graph diode

A

It will only allow the current in the forward direction . The arrow points positive to negative . It will not allow the current in the opposite direction because it has a high resistance. Direction depends on cell. Useful for Radio signals

24
Q

What is an LED

A

When the current passes through in the forward direction it emits light and uses a low amount of energy which is why they are used for lighting

25
Q

What is a thermistor

A

A thermistor raises or lowers the voltage and is used in heat sensors, radiators and ovens. The resistance decreases when the temperature increases, that is why they are used in baby incubators. If the temperature lowers a light will come on as a warning .

26
Q

What is an LDR

A

When it is brighter there is less resistance but when it is dark there is more resistance. Used for garden lights, street lights, when it gets darker the resistance increases and the bulb will turn on automatically.

27
Q

What are the names of the wires in a plug

A

Neutral
Earth
Live

28
Q

Colours of the wires

A

Blue
Green/yellow
Brown

29
Q

Live wire

A

This transfers the voltage from the power station to the appliance - 230v . It is very dangerous.

30
Q

Neutral

A

Transfers the current from the appliance back to the power station to complete a full circuit- just over 0v

31
Q

Earth

A

If there is a problem in the circuit it directs the electricity to the quickest route possible to the ground i.e. Not us - 0v THIS IS THE SAFETY WIRE

32
Q

Why do some appliances not need the earth wire

A

Because they have a plastic case

34
Q

What is the fuse

A

If there is a problem in the circuit and there is a large current it melts the wire and stops the electricity reducing injury

35
Q

Why are the pins made of brass

A

It is a good conducter of electricity

37
Q

Frequency in the U.K.

A

50Hz which means it changes direction and back again 50 times a second

38
Q

Voltage in the uk

A

230v

39
Q

AC current

A

Alternating current is used for mains electricity and power stations it constantly changed direction for the current

40
Q

DC current

A

Direct current is in batteries and cells it only flows in one direction .

41
Q

How to work out frequency on an oscilloscope for ac current

A

Frequency = 1 /time period

42
Q

Features in oscilloscope

A

Peak to peak voltage , period

43
Q

Why is an ac current graph up and down

A

There is a metal spinning in the coil of the wire

44
Q

Where does electricity come from

A

It comes from a power station via the national grid

45
Q

What is the national grid

A

A series of cables and transformers

46
Q

Step up transformer

A

Increases voltage

47
Q

Step down transformer

A

Decreases voltage

48
Q

Power station - 25000v
National grid- 132000v
House-230v
WHY IS THE VOLTAGE INCREASED 🔴🔴

A

We increase the voltage which lowers the current , this stops energy in cables being lost to heat
Cheaper to boost pd

49
Q

Benefits of increasing voltage in national grid

A

Less energy wasted
More efficient
Lower distribution costs
Cheaper for consumers

50
Q

Why live wire gives u an electric shock

A

Large voltage produced across body and current flows through you
Any connection between live and earth could be dangerous if the link creates a low resistance path to earth and cause a fire

51
Q

What does total energy transferred depend on

A

How long it’s on for and the power

52
Q

How do materials become when charged

A

This will leave materials electrically charged with positive static charge on one and an equal negative static charge on the other

53
Q

Polythene rod

A

Electrons move from the duster to the rod

54
Q

Acetate rod

A

Electrons move from the rod to the duster

55
Q

Electrostatic attraction and repulsion

A

When an object becomes charged by being rubbed against another object the objects will have equal and opposite charges

EQUAL CHARGES

56
Q

Electric fields

A

Created around any electrically charged object
Closer you get the stronger the field is
Further away is weaker

Go from positive to negative

Physics (3 decks)

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