Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
26 Cards in this Set
- Front
- Back
|
What is the unit if power |
kW |
|
|
What is the unit of time in hours |
Hrs |
|
|
What is the unit of units? |
kWhrs |
|
|
What is microgeneration? |
The use of wind turbines, solar power or any other domestic source of energy at home. Wind turbines use wind to produce electricity. They are unreliable as it is not always windy Photovoltaic cells are solar cells. They use sun light to produce electricity. They are unreliable because it is not always sunny. |
|
|
Why use microgeneration? |
Even though these are reliant on the weather and so are not reliable, they can save you money. For example: If too little energy is produced, (not windy or not sunny) then the grid will supply the energy. |
|
|
What is feed in tariffs? |
If you produce your own energy, the electricity supplier may pay you a Feed in Tariff for the electricity you supply. Also, if too much energy is produced, the consumer can 'sell it back' to the grid. In reality, the customer saves on the bill. Using microgeneration helps the national grid meet the energy demand if the country. |
|
|
What are the environment benefits of people creating their own energy? |
If people are using less power from the national grid, then less fossil fuels are burned which means less carbon dioxide and less global warming. |
|
|
What are the two types of current and what are they used for? |
AC and DC You use AC everyday, it comes from your plugs and DC is the electricity from a battery. |
|
|
What does AC and DC look like on a graph? |
|
|
|
What does the ring main look like? |
|
|
|
What is the ring main? |
All your plugs are connected on each floor via the ring main. If a fault occurs, the plugs and appliances will switch off for safety. They can be switched back on by a circuit breaker switch |
|
|
What is the live wire and what colour is it? |
Brown The function of the live wire is to carry the house/appliance at a high voltage |
|
|
What is the neutral wire and what colour is it? |
Blue Completes the circuit and carries currents away at low/zero voltage. |
|
|
What is the earth wire and what colour is it? |
Green and yellow stripes The wire is a safety wire that can carry current safely into the ground is a fault develops in a metal frames appliance |
|
|
What are the advantages of the ring main? |
The cables can be made thinner because there are two paths for the current. Each part of the cable carries less currents because the current flows to ways. A ring main circuit is more convenient since sockets can be placed anywhere on the ring: Each socket has 230V applied and they work seperately |
|
|
What is a fuse? |
A fuse is found in a plug connected to the live wire. It is designed to break when too much current passes through it. This may occur when a wire in the device touches the metal casing of the device causing a large current to pass to Earth |
|
|
What are the different Amps for fuses? |
3A, 9A and 13A |
|
|
Is a kettle had a power of 1.5 kW, what is the current of the device working at a voltage of 230V What fuse would you choose? |
P= 15kW = 1.5×10³ V= 230V I=? P=I×V 1.5×10³=I×230 1.5×10³ ----------- = I 230 6.5A=I Use a 9A fuse. It is just above 6.5A |
|
|
Using the earth wire with the fuse |
The earth wire is found in the plug and is used if an appliance has a METAL CASE If a fault occurs that causes the live wire to come in contact with the metal case of the appliance, then it will be dangerous to touch it. The earth wire carries the current away from you and to the fuse. The fuse them breaks and the appliance stops working The earth wire is connected to the metal case of the appliance |
|
|
What is an MCB |
Miniature circuit breaker This is an electromagnetic switch If too much current passes through the MCB a magnetic switch activates causing the appliance to be disconnected These are the trip switches found in the home |
|
|
What are RCCDs? |
Residual current circuit breaker A residual current circuit device detects a difference in the live and neutral wire current. They are different, they stop the device working. The RCCD protects the user rather than the device. A RCCD can be used if appliances are used outside where there may be damp conditions (e.g lawn mower) |
|
|
Advantages of using a MCB or a RCCD rather than a fuse |
It is more sensitive to current changes It is faster acting It can be reset |
|
|
The differences between MCB, RCCD and fuses |
MCB and RCCD can be reset and are fast working MCB and fuses protect the appliance from fire. RCCD protect the user and are most sensitive MCB and fuses only work when the user touches the case of an appliance that has a fault an so there is a risk of shock |
|
|
Topic 4- what is current? |
This is the flow of electrons around the circuit Current is measured in Amperes (A) It is measured using an ammeter in series with the components (wire, bulb ect) |
|
|
What is voltage? |
This is the push given to the electrons Voltage is measured in Volts (V) It is measured with a voltmeter in parallel with the components |
|
|
What is resistance? |
This opposes the current flow (it's in the opposite direction to current) It is measured in Ohms (_n_) We use an equation to find the resistance Resistance=Voltage ------------ Current |
