# Electricity

• Created by: 03Louise
• Created on: 24-04-18 18:23
• Electricity
• Current
• Flow of electrical charge
• Only does so when there's a potential difference and the circuit is complete
• Slowed down by resistance
• ohms
• Charge= current x time
• Potential difference
• Energy transferred= charge moved x potential difference
• Voltage
• Potential difference= current x resistance
• Resistance
• Increases with temperature
• Electrons collide with ions in the lattice giving them energy causing them to vibrate/ heat up
• Lead to it being harder for ions to get through
• Too hot- no current
• Circuit devices
• Resistors
• Current is directly proportional to p.d.
• Filament lamp
• Curved current/p.d. graph
• Diode
• No negative flow (high resistance)
• Light Dependent Resistor (LDR)
• Resistance is dependent on light
• Night lights, outdoor lighting, burglar detectors
• Hot= low resistance
• Thermistor
• Cold= high resistance
• Car engine temperature detectors, electronic thermostats
• Circuits
• Series
• Doesn't work if one part is removed
• More cells= bigger supply p.d.
• Current is the same everywhere
• More resistors= increased resistance
• Parallel
• If one thing is disconnected the circuit can still work
• How most things are connected
• Everyday circuits contain a mix
• All components have the same p.d
• Current is shared between branches
• If you add a second resistor in parallel to a series circuit overall resistance decreases to less than the smallest resistor
• Because the current has more than one direction to go in
• Energy
• When there's a p.d. energy is transferred as work is done against resistance
• Energy is supplied by the power source which is given up when going through components because of resistance
• Large p.d.- more energy is transferred
• E=IxVxt
• Kettle
• Transfer electrical energy to the thermal store
• Fan
• Electrical energy from the battery is transferred to the kinetic store
• Heating
• Temperature is too high- circuit melts
• Fuses use this to protect circuits
• Toasters use high resistance to heat up wires in the toaster creating infrared radiation
• Power
• Circuits
• Series
• Doesn't work if one part is removed
• More cells= bigger supply p.d.
• Current is the same everywhere
• More resistors= increased resistance
• Parallel
• If one thing is disconnected the circuit can still work
• How most things are connected
• Everyday circuits contain a mix
• All components have the same p.d
• Current is shared between branches
• If you add a second resistor in parallel to a series circuit overall resistance decreases to less than the smallest resistor
• Because the current has more than one direction to go in
• Energy
• When there's a p.d. energy is transferred as work is done against resistance
• Energy is supplied by the power source which is given up when going through components because of resistance
• Large p.d.- more energy is transferred
• E=IxVxt
• Kettle
• Transfer electrical energy to the thermal store
• Fan
• Electrical energy from the battery is transferred to the kinetic store
• Heating
• Temperature is too high- circuit melts
• Fuses use this to protect circuits
• Toasters use high resistance to heat up wires in the toaster creating infrared radiation
• Power
• Power(w)= Energy transferred(J) /Time(s)
• Energy transferred a second
• Power ratings
• Energy transferred a second
• Higher=more energy transferred a second/ uses more energy
• Power(w)= Current(A) x p.d(V)
• P=IV or P=I^2V
• Use to work out the fuse needed-just a little higher
• Power(w)= Energy transferred(J) /Time(s)
• Power ratings
• Higher=more energy transferred a second/ uses more energy
• Power(w)= Current(A) x p.d(V)
• P=IV or P=I^2V
• Use to work out the fuse needed-just a little higher
• Home
• Mains=a.c. (alternating current)
• Constantly changes direction
• 230V, 50Hz
• Cables
• Neutral
• Blue
• 0 V
• Completes the circuit, flows out
• Live
• Brown
• +/- 230 V
• Causes electrical shocks
• Body provides a path of low resistance to the earth- large p.d.
• Can cause fire
• Earth
• Green/yellow
• 0 V
• Carries away current if something goes wrong
• Appliance becomes live- prevents electrocution
• Untitled
• Only in appliances with metal casing
• Fuses
• Prevent surges which can cause melting, fire and electric shocks
• Live wire touches case
• Current flows through earth wire
• Creates a surge causing the fuse to melt breaking the circuit
• Prevents fires and electric shocks
• Household fuses
• Protect wiring in the house
• Circuit  breakers
• Work in the same way
• Large currents "trip" the fuse
• Can be reset, quicker but more expensive
• Large current =larger cable needed

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