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Physics GCSE AQA > P- 2- Electricity > Flashcards

P- 2- Electricity Flashcards

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1
Q
  • What is current
A
  • The flow of Electrical charge

- Measured in Amps

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2
Q

_ What is needed to make electrical charge flow

A
  • Complete circuit

- Potential difference

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3
Q
  • What is potential difference
A
  • Force that pushes the charge- volt
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4
Q
  • What is the distribution of current around a full circuit
A
  • Even at every point
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5
Q
  • What is resistance
A
  • Anything that slows the flow down

- Measured in ohmes

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6
Q
  • What does current depend own
A
  • Potential difference and resistance
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7
Q

What does total charge depend on

A
  • Current and time
  • Q= It
  • Charge flow = current x time
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8
Q

What are the symbols of cell and resistor

A

Cell - —-±||—–

Resistor ——| |——–

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9
Q

What are the symbols for battery and variable resistor

A

Battery ——±| |——-±| |——-

Variable resistor —|_/|

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10
Q

What are the symbol for switch open and ammeter

A

Switch open- ___./ ._____

Ammeter - A - in circle

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11
Q
  • What are the symbols for voltmeter and switch closed
A
  • Switch closed- __.__.___

- Voltmeter- —V—- In circle

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12
Q

What are the symbols for filament lamp and diode

A

Filament - —-x—- - In circle

Diode- —–|>|— In circle

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13
Q

What re the symbols for fuse and LDR

A
  • Fuse - ——|——-|——-

    LDR- —–|___|——–
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14
Q
  • Wat are the symbol;s for LED and thermistor
A 
//
- LED- ---|>|-----

Thermistor—-|_/___|——-
_/

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15
Q
  • What is the formal for potential difference and current
A
  • Potential difference = Current x resistance
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16
Q
  • How can you investigate resistance factors
A
  • Wire length
  • Attach crocodile clip to wire at 0cm
  • Attach second crocodile clip to wire - writer down length between
  • Close switch and mature current and PD
  • Open switch and move along a fixed measurement and retest- repeat
  • Use measurement and calculate resistance using formula
    • Polt graph- should be directly proportionate
  • IF not may be a systematic error e.g first clip not at 0
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17
Q
  • What its the ammeter
A
  • Measures current in amps flowing through a wore

- Placed in series with what you are doing

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18
Q
  • What is a voltmeter
A
  • Potential difference across test wire

- Must always be placed in parallel around what you are testing - not around any other

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19
Q
  • What happens in resonance of Ohomic conductors
A
  • It does not change with current
  • e.g wire or resistor
  • at constan temp current flowing is directly proportionate t potential difference
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20
Q
  • What happens in appliances where resistance changes
A
  • e.g diode and filament lam
  • Filament- - transfers energy to thermal store - heats up - resistance increases with temperature - as current increases so does resistance
  • Diode- Depends on direction of current - very high resistance if reversed
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21
Q

what are I- v Characteristics

A
  • Refers to a graph which shows how current flowing through changes as potential difference increases
  • Linear components I-v are straight ;owed-
    -Non linear- Curved
    -
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22
Q
  • How can you test for the I-v Characteristics
A
  • Set up test circuit with variable resistor, component, ammeter, voltmeter, component and battery
  • Begin to vary variable resistor- alters current flowing an potential difference
  • Take several pairs of readings from ammeter and voltmeter- to see how potential difference varies as current varied- repeat and get average
  • Swap over wires so its reversed
  • Plot a graph of current against voltage
23
Q
  • What do I-v Characteristic s look like for , ohmic conductors, filament lamps and diodes
A
  • Ohomic- Straight- linear
  • Filament- Curved going both under and over
  • Diode- Only appears in positive and steep
24
Q

What is LDR

A
  • Light dependant resistor
  • Dependent on intensity of light
  • Bright light causes resistance to fall
  • Darkness - resistance is highest
  • e.g Automatic night lights and burglar detectors
25
Q

-What is a thermistor

A
  • Temperature dependant resistor
  • Hot conditions cause resistance to drop
  • Cool conditions cause increase in resistance
  • Good tematyre sectors e.g car engines
26
Q

What can sensing circuits be used for and how

A
  • Turn on or increase power to components depending on conditions
  • Fixed resistor will always have the same potential difference as there connected in parallel
  • PD is shared between thermistor and loop according to resistance - bigger resistance means more PD
  • As it become shorter Resistance of thermistor decreases- more PD to fan- Fan goes faster when its hotter
27
Q

What are sires circuits

A
  • Different comments are connected in a line end to end, between =ve and -ve of power supply - except voltmeters
  • If you remove or disconnect one component the circuit is broken- not very practical
  • Measure quantities and test components
28
Q
  • What are the characteristics of a sires circuit
A
  • Potential different is shared- always add unto source
  • Current is equal everywhere - size of current is determined by total PD of cells and total resistance of circuits - I = V//R
  • Resistance adds up- total resistance adds together to find ass- as they have to share PD- Total current is reduced when resistor is added - bigger resistance is the bigger its share
29
Q
  • Give a worked example for finding current passing through as 20 volt circuit with one 2 Ohme resistor and a 3 homes resistor
A
  • Resistance total + 5 Ohmes
  • I= V= R

20//5

+ 4A

30
Q
  • What are parallel circuits
A
  • Each component is separate;y connected to +VE and -VE of Supply- except ammeters
  • If you remove or add one nothing changes
  • Most things connected this way
31
Q
  • What are the characteristics of a parallel circuit
A
  • All components get full source of PD- PD same across all components- means all bulls are same brightness
  • Current is shared- Total current = total of current in all other components
  • Junctions where current splits or junctions- HAs to be equal to current leaving
  • IF identical components are connected they all have the same current
  • Adding a resistor reduces total resistance- IF you have two their total resistance is less than resistance of smallest of two resistor
32
Q

-How do you investigate the effect of adding resistors in Siries circuits

A
  • Need four identical resistors
  • Build circuit using one resistor- make not of PD
  • Measure current- Calculate resistance to measure current
  • Add another resistor and measure current
  • Repeat
  • Plot
  • Should follow linear positive
33
Q
  • What can you do to investigate effect off restores in Parallel circuits
A
  • Set up parallel circuit
  • Need four identical resistors
  • Measure total current and calculate current using resistance- V being PD of battery
  • Add restore sea repeat
  • Plot graph
  • Should follow non direct proportional negative lines- that follows the diminishing returns
34
Q
  • What is alternating current
A
  • Current is constantly changing directions
    _ Produced by alternating voltages- positive and negative is costly switching
  • Uk mains ac supply is 230 - 50 HZ- or cycles per seconds
35
Q
  • What is direct current
A
  • Current laws flowing in same direction
  • Created by direct voltage
  • Batteries
36
Q
  • How are most cables in plugs structured
A
  • 3 sperate wires - Core of copper and coloured plastic stating
  • Colour of insulation on each cable shows purpose - always sa,e
37
Q
  • What are the three parts of the club and there function
A
  • Natural wire - Blue- Complete circuit and carries away current- Normally flows in through live and out though neutral
  • Live- Brown - Provides alternating potential difference- 230v- flows into
  • Earth wire- green and yellow- Protecting wire and safety- stops appliance casing from becoming live- no current usually
38
Q
  • How can live wire give a shock
A
  • Large potential differences produced across body and current flows through you
  • Causes shock that may kill you
  • Even if its off - there is still POD and a risk of a shock- Body would provide link and current flows through you
  • Any connection between li e and earth can be dangerous. Link may create path top earth and huge current would flow- causing a fire
39
Q
  • How is energy transferred
A
  • From cells and other courts
  • Moving charge transfers energy as charge works against resistance
  • Electrical appliances are designed to transfer energy to components
40
Q
  • Give tow examples of how appliances
A
  • Kettles transfer electrical from mains into thermal to heating element
  • handheld fan- Electric from battery into kinetic
  • Not all useful- higher current causes higher amounts of thermal energy transfer
41
Q
  • What does energy transferred depend on
A
  • Power

- Toal energy by an appliance depends how long the appliance is on for and its oiler

42
Q
  • What is power
A
  • Is energy that it transferred per second

- More energy means more power

43
Q
  • How can you work out energy transferred
A
  • Energy transferred = Power x time

E=Pt

44
Q

What is a power rating

A
  • labelled with maximum safe oiler they can operate at
  • Maximum amount of energy transfer between stores per second
  • Helps customer choose- lower power ratings- less electricity is uses- cheaper
  • Higher power rating does not mean more energy is transferred - fails to address usefulness of energy transferred
45
Q
  • What is potential difference
A
  • Energy transferred per charged passed
  • When electrical charge goes through a change in potential difference then energy is transferred
  • Energy supplied to charge at power source to raise it through a potential
  • ## The charge gives up this energy where it falls through any potential drop in components
46
Q
  • What is the formula for potential difference
A
  • Energy transferred = Charge flow x potential difference
    E= QV

-

47
Q
  • What does a battery with a lager PD mean
A
  • Will supply more energy for every coulomb of charge which flows around it, because charge is raised higher at the start
48
Q
  • How does power depend in current and potential difference
A
  • Power = Potential difference x current
  • if you don’t know potential difference you can rearrange to get P= I2R
  • R- resistance
49
Q
  • How is electrify distributed
A
  • Via the national grid
    • giant system of cables and transformers that covers Uk and connects power stations to consumers
  • National grid transferred electrical power from power stations to demand
50
Q
  • What does production have to meet
A
  • Demand
  • usage changes throughout day- power stations have to keep up with this demand
  • Can predict when demand is highest- e.g time of day or big event
  • Many run far below maximum power output so they can always meet high demand
  • Lots of power stations that are smaller can open up fast if in need
51
Q
  • What does the national grid use
A
  • High potential difference and low current
  • To transmit he amount of power you need either high
  • Problem with high current is you lose loaf of energy to thermal loss
    0 Most chapter to boost PD to 400,000 and keep current low
    – mAke it very efficient
52
Q
  • How is potential difference impacted by transformers
A
  • To get to such a high PD requires transformers as well and big pylons and huge insulators - but its still cheaper
  • The transformer shave to step the potential difference up at one end and down to a usable level at another
53
Q
  • How is potential difference increased and reduced
A
  • PD increased using step up transformer

- Reduced using step down transformer

Physics GCSE AQA (8 decks)

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