P2 - Electricty - Revision - GCSE Flashcards by Counter Time

Keywords
Define voltage

Energy per charge

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Keywords
Define current

The rate of flow of charge

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Keywords
Define plug

Connects appliances to the mains

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Define earth wire

Safety wire that prevents an appliance becoming live by redirecting excess current to the ground

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Define neutral wire

Completes the circuit

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Define live wire

Carries electricity from the mains to the appliance

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Define static electricity

Charge that accumulates on an insulated object due to things such as friction

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Keywords - circuit components
Bulb

Lights up when current passes through

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Keywords - circuit components
Voltmeter

Measures potential difference (in volts)

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Keywords - circuit components
Ammeter

Measures current (in amps)

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Keywords - circuit components
Cell/battery

Provides a potential difference in a circuit

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Keywords - circuit components
Switch

Turns circuit on and off by breaking or completing it

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Keywords - circuit components
Resistor

Provides resistance - making it more difficult for current to flow

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Keywords - circuit components
Variable resistor

Provides a changeable resistance

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Keywords - circuit components
Fuse

Heats up and melts, breaking the circuit, when current is too high

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Keywords - circuit components
Diode

Keeps current flowing in one direction

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Keywords - circuit components
Thermistor

Changes resistance based on temperature, decreasing resistance when temperature increases

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Keywords - circuit components
Light dependent resistor

Changes resistance based on light, resistance decreases when light intensity increases

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Keywords - circuit components
Have you revised circuit symbols?

Yes

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Circuits - properties
What is the equation for current, charge and time? (Hint: derive it from the definition of current)
Give units as well

I = Q / t
I - Amps
Q - Coulombs (C)
t - time (s)

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Circuits - properties
What does charge do?

Carries energy from the battery to circuit components

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Circuits - properties
What is the bread - bakery model of circuits?

Bread goes from bakery to shop on vans and roads in the same way charge travels round a circuit to components

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Circuits - properties
Define a parallel circuit

A circuit in which there is more than one pathway for current to flow

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Circuits - properties
Define series circuit

A circuit where there is one pathway for current to flow

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Circuits - properties What happens to current in a series circuit?

Stays equal throughout

Circuits - properties What happens to current in a parallel circuit?

It splits across branches

Circuits - properties What happens to potential difference in a series circuit?

It splits across components

Circuits - properties What happens to potential difference across a parallel circuit

It stays equal on each branch

Circuits - properties What is the total resistance in a series circuit?

Sum of each resistors’ resistances

Circuits - properties What is the sum of resistance in a parallel circuit?

Less than the resistance of the smallest resistor

Circuits - properties Give the equation for voltage (hint: it is derivable from the definition of voltage) And give units

V = E/Q V - volts - V E - Energy - Joules - J Q - Charge - Coulombs - C

Circuits - properties What is ohms law (equation and explanations) Give units as well

V = I R V - volts - V I - Current - Amps - A R - resistance - Ohms - Ω Voltage is directly proportional to current with constant current (and proportional to resistance with constant current) Resistance is inversely proportional to current

Circuits - properties Give the 2x equations for power and the equation you use to derive it Give units as well

P = I V P = E / t P - Watts - W I - Current - Amps - A V - Voltage - Volts - V P = I squared x Resistance I - current - Amps Resistance - Ohms - Ω

Required practicals - resistance and length of wire What are the independent, control and dependent variables in the investigation?

Independent - length of wire Dependent - resistance Control - current, voltage, wire temperate and thickness

Required practicals - resistance and length of wire Write the method for this investigation

Fix crocodile clips to bare wire 10 cm apart Get ammeter and voltmeter readings (to find initial resistance) Disconnect the circuit and increase the distance between the crocodile clips by 10cm - wait 10 secs Connect and get ammeter and voltmeter readings Repeat until 100cm Draw a graph of voltage and current (voltage on y axis as resistance should be the gradient)

Required practicals - resistance and length of wire What should the conclusion of the investigation be?

Resistance and length of wire are directly proportional (as length of wire increases so does resistance)

Required practicals - ohms law on a resistor What components do you need to set up this circuit?

Resistor, variable resistor, voltmeter attached in parallel on the resistor, battery, switch

Required practicals - resistance and length of wire True or false: you should connect the voltmeter in parallel measuring the potential difference of the bare wire in the investigation

True

Required practicals - ohms law on a resistor Write a method for this investigation

1. Set variable resistor on lowest resistance 2. Record voltage and ammeter readings 3. Increase resistance incrementally (1 Ω segments) 4. Repeat at least 6 times Plot the graph

Required practicals - ohms law on a resistor What should the conclusion of this investigation be?

That ohms law applies on a resistor (it is an ohmic conductor)

Required practicals - resistance in series vs parallel circuits What components to you need in this circuit

Resistance x 2, voltmeter, ammeter, switch, battery

Required practicals - resistance in series vs parallel circuits What is the independent, control, dependent variable in the investigation

Independent - arrangement of the resistors Control - resistor, battery, voltage, length of wire Dependent - total resistance in the circuit

Required practicals - resistance in series vs parallel circuits Write the method for the investigation

1. Take a reading of current and voltage in a series arrangement 2. Take the same readings in a parallel arrangement 3. Compare results

Required practicals - resistance in series vs parallel circuits What should the conclusion be for the investigation?

Resistance is higher in a series circuit (sum of resistance of resistors) than parallel (less than the lowest resistor)

Required practicals - Ohms law in different components Does a bulb follow ohms law - draw the graph of a filament bulb and plot voltage and current

Required practicals - Ohms law in different components Why doesn’t a bulb follow ohms law

It heats up and this increases resistance through the movement of positive metal ions preventing the movement of electrons throughout the circuit

Required practicals - Ohms law in different components Does a diode follow ohms law

Required practicals - Ohms law in different components Why doesn’t a diode follow ohms law - draw a graph of it with respect to voltage and current

It has very high resistance in one direction, so current is zero there. It also high high resistance at low potential differences, which means current stays low initially

Required practicals - Ohms law in different components What is one hazard which is pretty much universally applicable when talking about investigations

Hazard - hot wire Consequence/risk - burns skin Precaution / control measure - don’t touch the wire when the circuit is connected and allow it to cool

Exam - Required practicals - Ohms law in different components How do you structure questions that ask about how to minimise risk or take precautions in experiments

To prevent (risk) … which would cause (hazard) … we should (preventative measure) …

Plugs + mains What are pins made of in a plug? Why?

Brass - tough, durable, conducts electricity, doesn’t rust!!!

Plugs + mains What are wires made of?- why?

Copper - conducts electricity, bends and is ductile, cheaper than alternatives like gold

Plugs + mains What is the casing of a plug made of - why?

Plastic - doesn’t conduct (insulator), durable and tough

Plugs + mains What colour is an earth wire

Striped yellow and green

Plugs + mains What is the colour of a neutral wire

Blue

Plugs + mains What is the colour of a live wire

Brown

Plugs + mains Where does the earth wire go

Top - think striped (see. Mindmap)

Plugs + mains Where does the live wire go

Right - see mindmap for rule

Plugs + mains Where does the neutral wire go

Left - see mindmap for rule

Plugs + mains What are the 3 main ratings of fuses

3 A, 5 A and 13 A

Plugs + mains What is the rating of a fuse

The maximum current that can go through a fuse without it blowing

Plugs + mains What is it called when a fuse heats up and melts

The fuse has blown

National grid What is the first stage of the grid (and bonus for its voltage)

Power station - 25kV

Plugs + mains What is a step up transformer and why does it do what it does

Increases voltage, decreasing current to make the system more efficient - as it prevents energy dissipating into the surroundings

Plugs + mains True or false: pylons and cables have high current and low voltage - with a voltage of 132 kV

False (it is the opposite) - however the voltage is still 132 kV

Plugs + mains What does a step down transformer do and why?

Increases current and decreases voltage, to make voltage safe

Plugs + mains What is the voltage of the mains

230V

Plugs + mains What is a power station definition

Generates electricity which is then transported around the country

Plugs + mains What are pylons

They support electric cables

Plugs + mains What do cables do

Transports electricity around the country

Plugs + mains What is the role of transformers

Increases and decrease voltage at particular stages in the national grid

Plugs + mains Give 3 pros of overhead cables

Cheap and efficient, easy to repair, can cross roads and canals easily

Plugs + mains What are 3 cons of overhead cables

Visual pollution, prone to decay, takes up space

Plugs + mains What is one pro of underground cables and find a bonus one

No visual pollution - and decays less easily than overhead cables

Plugs + mains What are 3 cons of underground cables

Expensive, difficult to repair, difficult to bury around canals and roads

Static electricity What is static electricity

Charge that accumulates on insulators due to forces like friction

Static electricity How can static electricity be produced?

Rubbing materials together - this means some negative charge is lost from one material as it is dislodged by the force of friction, and given to another

Static electricity Which way does a positive electric field point

Outwards