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Physics - P2 - Electricity, Key: - Coggle Diagram
Physics - P2 - Electricity
Energy transfers
Power
Power = Energy transferred/ time in seconds
1 Watt = 1 J/s
P=E/t
Power = W ( Watts)
Energy transferred = J ( Joules)
Time = s (seconds)
Power = potential difference ( p.d in volts) x Current ( in amps)
P = I*V
Power = W ( Watts
Current = A (Amps)
Potential difference = Volts ( V)
Power = Current ^2 x Resistance
Power = Watts
Current = Amps
Resistance = Ohms (Ω)
Power Ratings
A device with a higher power rating will transfer stored energy to other types of energy at a faster rate
The table
Appliance - Power in W or Power in kW
Clock - 10 or 0.01
Lamp - 50 or 0.05
Drill - 800 or 0.8
Iron - 1,250 or 1.25
Kettle - 2,400 or 2.4
Hot water heater - 3,000 or 3
Electric oven - 12,000 or 12
The National Grid
A system of cables and transformers linking power stations to consumers.
Step down transformers
Decreases voltage for safe dometic use.
Step down transformers have more turns on the primary coil than on the secondary coil.
Step up transformers
Used to increase voltage to decreased dissipated energy in the form of heat.
Step up transformers have more turns on the secondary coil than the primary coil
Uses alternating current as it needs changing magnetic field in order to work.
Voltage increase from 20000v to 400000v in step up transformers
Decreased to 230 volts for safe domestic use.
Energy transfers in everyday appliances
Torches.
Chemical store in the battery :arrow_right: thermal store (heating up of filament in bulb to produce light)
The amount of energy depends on the length of time the appliance is used for
Vacuum cleaner
Energy transferred from power stations ( as vacuum run off mains electricity)
Chemical store of coal ( fuel for power stations) :arrow_right:
via heating pathway
Thermal store ( wasted energy on heat)
Via electrical pathway
Kinetic store of motor ( useful)
Also has wasted energy of sound.
Work is done when charge flows around a circuit
Energy transferred can be calculate using these equations
Energy transferred = charge ( coulombs/ C) x potential difference (volts/ V)
E=Q*V
Energy transferred = power ( Watts/ W) x time ( second/s)
E=P*t
Efficiency
Power
Efficiency = Useful power output ( transferred) / Total power input (supplied)
Percentage efficiency = efficiency x 100
Energy transferred
Percentage efficiency = Useful output energy / total Input energy x 100
Static electricity (physics)
Static charge
Friction causes the transfer of electrons from one surface to another. This causes them to become charged depending on whether it is losing or gaining electrons.
Electric fields
A charged object creates an electric field around it
Like a magnetic field the further away from the charged object you go the weaker the electric field
Current, potential difference and resistance
Standard circuit diagram symbols
Electrical charge and current
Resistance
Current, resistance and potential difference
Domestic uses and safety
Direct and alternating potential difference
Mains electricity
Series and parallel circuits
Key:
Major focus of exam
Small part of exam
Not assessed in exam
