P2 electricity Flashcards

1
Q

Static electricity

A

Insulators cause a build up of charge. When it flows to a conductors you get a shock.
Charged by friction

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2
Q

Electron transfer

A

An atom consists of a small positively charged nucleus surrounded by negativity charged electrons. In a neutral atom direct equal numbers of positive and negative charges. All electrostatic effects are caused by the movement of electrons

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3
Q

Electric field

A

A region where a force acts on a charged particle

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4
Q

Field

A

A region of space where a force can act at a distance

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5
Q

Strength of an electric field

A

The closer to the centre the stronger it is

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6
Q

Sparking

A

Air is an electrical insulator not conductor
However when there are very strong electric field the atoms and molecules in the air break apart to form positive and negative ions
Charged ions experience force from the field and move
Creating a spark

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7
Q

Electric current

A

The rate of flow of electric charge from negative to positive

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8
Q

Electric charge

A

Is measured in coulombs

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9
Q

Potential difference

A

The energy transferred per unit charge as charges move between 2 points in a circuit. It is measured in volts using a voltmeter which is always connected in parallel

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10
Q

Resistance

A

Electrons collide with metal ions in the resistor
Energy transferred to metal ions so vibrate and resistor gets hotter
Increased vibrations of ions in fixed lattice makes it harder for electrons to travel through so resistance increases

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11
Q

Series circuit

A

Components connected next to each other in a single loop

Lamps shine duller

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12
Q

Parallel circuit

A

Components are connected to each other like rungs in a ladder
Lamps shine brighter

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13
Q

Resistors in series

A

R1 and R2 has the same current as the current has to pass through both of them
Total resistance is R1+R2
Have same pd that combined is the of of battery
Resistors increase total resistance

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14
Q

Resistors in parallel

A

Current can either pass through R1 or R2 meaning the ammeter reading is A1 equal to the sum of A2+A3
Pd of battery is the same as pd across each component
V1+V2 are the same and = of of battery
Resistors decrease total resistance

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15
Q

Parallel calculations

A

Pd is identical across each resistor

Current is sum of currents that pass through each resistors

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16
Q

Series calculations

A

Pd is sum of all pd across resistors

Current is same through all resistors

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17
Q

Measuring resistance of resistor

A

Battery,variable resistor,resistor,voltmeter, ammeter

Straight line through origin, ohmic conductor

18
Q

Measuring resistance of filament lamp

A

Battery,variable resistor,resistor,voltmeter, ammeter

Upside down curve non ohmic conductor

19
Q

Required practical – investigate, using circuit diagrams to construct circuits, the IV characteristics of a filament lamp,a diode and a resistor at constant temperature

A

2 variables-pd and current
0-12 V dc, voltmeter,component,ammeter and variable resistor
Resistor is ohmic (straight line)
Filament lamp isn’t ohmic (s shape)
Diode isn’t ohmic (straight line then increases)

20
Q

Required practical – use circuit diagrams to set up and check appropriate circuits to investigate the factors affecting the resistance of electrical circuits, including the Length of a wire at a constant temperature and combinations of resistors in series and parallel

A
0-12 V dc battery, component, voltmeter, ammeter and variable resistor 
Find pd & current of each length 
Plot on a graph 
Do this in series by adding component 
For parallel Add components in parallel
21
Q

Sensors

A

Detect changes in the circuit

22
Q

Thermistor

A

A light dependant resistor. Resistance changes a lot as temperature changes
Low temp= high resistance
High temp= low resistance
2000 ohms at -20 degrees
200 ohms at 20 degrees
Made from a semi conductor (not insulator or conductor)

23
Q

Light dependant resistor

LDR

A

Resistance changes a lot as light intensity changes
Bright= resistance low
Dark= resistance high

24
Q

Uses of thermistors

A

Turn on heating when it gets cold
Fire alarm
Stop fish tank getting too cold

25
Q

Uses of LDRs

A

Simple light meter

Used in cricket to see if it is too dark to play or not

26
Q

Diode

A

Only allows current to flow in one direction. The direction the arrow points to
Most start to conduct pd at 0.6V

27
Q

A cell has 2 terminals

A

Positive and negative

Current is dc (Always passes in same direction)

28
Q

Mains electricity differs in 2 ways

A

Current alternates at a frequency of 50Hz

It has a much higher potential difference 230 V

29
Q

Live wire

A

Brown wire
Connect to house
Carries high pd into and around the house
Fuse in plug is always connected to live wire

30
Q

Neutral wire

A

Blue wire
Return path to local sub station
Is earthed so close to earth potential
No current in wire till electrical appliance is connected

31
Q

Earth wire

A
Yellow/green striped wire
Safety wire 
Connected to wire case of an appliance to prevent it being charged of touched by live wire
Low resistance path to ground 
Normally no current in it
32
Q

National grid

A

A collection of power cables and transformers that connect power stations to factories and houses across Britain

33
Q

Changing the pd

A

Domestic uk mains supply 230V
Electrical power is transmitted across the country at 400000V
Pd between live and earth is very big
The higher the pd the lower the current
The lower the current the less energy lost as heat

34
Q

Transformers

A

Devices that can change the pd
Made with 2 coils of wire with some iron passing between them
Varying number of turns on coil changes pd

35
Q

Step up transformers

A

Increase pd

Connected between power stations and the national grid

36
Q

Step down transformers

A

Decrease pd

37
Q

Power

A

The amount of energy transferred each second

38
Q

When charge flows in a circuit

A

Electrical work is done

39
Q

Power transfer

A

Potential difference across it and the current passing through it

40
Q

Current

A

A flow of charge

41
Q

Potential difference

A

Work done by moving a unit of charge

Energy transferred

42
Q

Resistance

A

How hard the current is being opposed