Chapter 5 Electricity In The Home Flashcards
(26 cards)
How are devices that use plugs and devices that use batteries are different? (2)
Batteries use DC current and plugged devices use AC current
Batteries transfer energy from chemical potential by electric current, plugs directly supply electrical energy.
How devices that use plugs and devices that use batteries are the same? (2)
Both transfer energy to electrical devices
Both must be connected to the device
What is DC (Direct current)
Where current flows in one direction only (cells and batteries)
What is AC (Alternating current)
Where current constantly changes direction, how often is called frequency (mains supply,the power socket)
What is Mains Electricity and what it’s features
Mains Electricity refers to the electricity supplied to homes and businesses from power stations. And is alternating current (a.c). With the uk mains electricity about 230V and has a frequency of 50Hz
What is the Frequency time equation(inversely proportional)
Frequency = 1 / Periodic Time = 1/T Hertz
f=1/T Hertz
How do people get electricity in their homes
From the national grid whats a network of cables, pylons and transformers used to transfer electricity from power stations to consumers
What are step up and down transformers
Step up: used at power stations to transfer energy to the national grid, which increase the size of the alternating potential difference to around 25,000-132,000V
Step down: used to supply energy from national grid to consumers, supply energy with power of 230V and factories 33KV-100KV
Why do we use transformers
As it increases the potential difference which decreases the current so then less energy lost due to hear so more efficient to transfer power around the country
3 purposes of plug and cable on an applicance
-Ensures safety
-Conducts electricty
-Insulation for protection
3 materials of plug and why its used
Brass pin- good conductor of electricity and does not rust or oxidise and harder than copper.
Plastic case- electrical insulator and shaped that that the wires and pins cannot touch
Copper wire- Copper an excellent conductor of electricity and bends. easily
Main parts of the plug (5 parts)
Earth wire
Neutral wire
Cable grip
Live wire
Fuse
Different colour wires and their purpose
Live wire(brown) - carries current to the appliance at a high voltage
Neutral wire(blue) - completes the circuit and carries current away from the appliance
Earth wire(green and yellow) - safety feature connecting the metal case of am appliance to the earth so the appliance isn’t live
What does the fuse do
It melts and break the wire due to the current being too strong, circuit is broken and stops working
Difference between 3 and 2 core cable
3 core - appliance has a metal case with earth wire connected to longest pin. If the live wire touches the case it’s earthed and case doesn’t become live itself - like a toaster
2 core - appliance has a plastic wire. No earth wire as the case is an insulator. If live wire touched the case then the case does not become live - like a hairdryer or radio
What is a short circuit
If a live wire touches a neutral wire a very big current passes at point of contact and normally blows cutting the current off
What happens if someone touches a live wire
A massive potential difference acts across your body causing a current to flow through you, could be lethal.
What is electrical power
The rate of energy transfer by each electrical component
Electrical power equation
Power = Energy / Time
P(watts) = E(joules) / T(seconds)
What is the second equation for electrical power
Power = Current X Potential Difference
P(watts) = I(amperes) X v(volts)
If you don’t know the voltage how to calculate power and the equations
Use resistance and current
Power = Current^2 X Resistance
P(watts) = I^2(amperes) X R(ohms)
What is charge flow (3 facts)
In circuit electrons forced through components by the potential difference of battery or cell. Charge is carried through by the electrons which is negative
Equation to calculate Charge
Charge flow = current X time
Q(coulombs) = I(amperes) X t(seconds)
2 things what can affect how hot the resistor gets
- the amount of charge that paddes through it each second
- the potential difference across the resistor
