Electricity

What’s a circuit

A closed loop with a power source and something for electrons to flow through

What is a battery

2 or more cells

When a switch is open in an circuit, what happens

Break the circuit so current can no longer flow

What is potential difference (V)

The force driving the flow of electrons

• provided by the cell or battery

• Voltage → measure in volts (V)

What is current (I)

A measure of the flow of electrons around the circuit

• measured in amperes (A)

What is resistance (R)

Everything that opposes the flow of electrons

• measured in ohms

What way does a circuit flow

Positive to negative → called conventional current

What’s the equations for potential difference/ voltage

Potential difference = current x resistance

V= I R

Is resistance stays constant and P.D increases, what happens to the current

Is should increase proportionally

What happens to the line on a graph if you use a small or bigger resistor

Smaller resistor = steeper line

Bigger resistor = flatter line

what is charge / voltage

The measure it total current that flowed within g a period of time

• units are coulombs ( c )

What’s the equation for charge

Charge= current x time

Q = I x t

What does a light emitting diode do

• only allow current to flow in one direction

• Emit light when current flows through it

What are ammeters

• measure current

• Added to a circuit in series

What’s a voltmeter

• measure potential difference

• Added to a circuit in parallel

What’s a thermistor

A resistor whose resistance decreases when temperature increases

What does a variable resistor do

Adjust resistance easily

What is a fixed resistor

A resistor which cannot vary the amount of resistance it provides

What does a light dependant resistor do

A resistor that resistance varies with light intensity

When does the resistance of a thermistor decrease

When temperature increases

What’s a series circuit

• single loop

• Potential difference is shared across all of the components

• Current is the same everywhere

• The total resistance is equal to the sun if the individual resistances of each components

• Components with a greater resistance will always have a greater share of the voltage

What’s a parallel circuit

• More than one loop

• same potential difference

• Total current is shared between all of the parallel loops

• The sum is the current in each loop is equal to the total current

• Adding a resistor in parallel with an existing resistor will decrease the overall resistance

What’s ohms law

Describes the relationship between voltage, current and resistance

• V=IR

What’s the 3 formulas for energy

E=Pt

E=V x I x t

E=QV

E= energy P= power T= time V= voltage I= current Q= charge

What are the two different formulas for power

P= IV

P=I² x R

P=power, I=current, V=voltage, R=resistance

How do fossil fuels and nuclear power stations work

• generates thermal energy

• Used to turn water into steam which can then rise and turn turbines

• Kinetic energy of the moving turbines can be converted to electrical energy,

• which is finally sent to the national grid

When electricity demands vary during the day, when do they generally peak

Late afternoon

When transmitting electricity what does a HIGH current generate

• wasted heat

• High currents cause the wire to heat up, meaning that energy is lost as heat to the surroundings

What are step up transformers used to do

Increase the voltage and decrease the current

What are step down transformers used to do

Decrease the voltage and increase th3 current

How does electric power get to our homes

1. Electric power is generated at a power station

2. Step up transformers increase the voltage and decrease the current

3. The electric power is transmitted via the national grid at low currents to minimal use power loss

4. Step down transformers decrease the voltage and increase the current near our home

5. Electric power is wired into our homes at a voltage that is relatively safe to use

What is alternating current

type of current that periodically reverses direction (alternates direction)

What’s direct current

When charge always flows around a circuit in the same direction

What causes an AC

Alternating potential difference

What is DC supplied by

Cells and batteries

What is the UKs mains supply’s frequency and voltage

Alternating current

50 Hz

230V

What does an oscilloscopes role

Display how voltage changes with time

What are the 3 wires in plugs

• earth wire

• Neutral wire

• Live wire

What are wires made of

Made of copper and coated in a layer of insulating plastic

What the earth wire

• yellow and green

• Doesn’t carry current

• P.d of 0

• Stops the casing from becoming live as it provides an alternative pathway fir the current to flow away

Whats the neutral wire

• blue

• Completes the circuit by carrying away current

• P.d of 0v

What the live wire

• brown

• Provides alternating p.d of 230 v from main supply

What wire prevents electrical casing from becoming live

Earth wire

What wire supplies current to the appliance

Live wire

What old do humans have

P.d of 0

• if we touched live wire a large current would flow through us as a electric shock because live wires have a large p.d of 230v

Whats a surge

Sudden increase in current

How does a surge happen

• when there are changes in an appliance, like turning it on or off

• Fault in circuit or appliance

What can surges cause

• fires

• Electric shocks

What are some safety precautions fir surges

• fuses

• Earth wires

• Circuit breakers

• Double insulation