Electricity Flashcards
What is direct current (d.c)?
The current only flows in one direction and is produced by a direct potential difference.
What provides direct current?
A cell or battery.
What provides an alternating current?
Mains electricity.
What is alternating current (a.c)?
The current repeatedly reverses direction and is produced by an alternating potential difference.
What is the frequency of the mains electricity supply in the UK?
50Hz.
What is the voltage of the mains electricity supply in the UK?
230V.
What is the colour of the live wire in a plug?
Brown.
What is the colour of the neutral wire in a plug?
Blue.
What is the colour of the earth wire in a plug?
Green/yellow.
What does the fuse in a plug do?
It melts and blows if too much current flows after the live wire touches the neutral wire.
What is the role of the neutral wire?
Provides a return path for the current to the
substation.
What is the role of the earth wire?
A safety wire to prevent the appliance from becoming live and provides a low resistance path to the ground.
What is the potential difference of the live wire?
230v
What is the potential difference of the neutral wire?
0v
What is the potential difference of the earth wire?
0v and only carries current if there is a fault.
What is used the wire coatings in a plug and why?
Plastic because its a good electrical insulator.
What is used for the wires in a three-core cable and why?
Copper because its a good electrical insulator and bends easily.
What is the National Grid?
A network of cables and transformers that carries the electricity generated by power stations and renewable energy generators to homes and other buildings.
What are transformers?
Devices that can change the potential difference of an alternating current.
How much do power stations produce electricity at an alternating potential difference of?
25,000v.
How much electrical power do the cables in the National Grid transfer?
400,000v.
What are step-up transformers used for?
Used to increase the potential difference from the power station to the transmission cables.
What are step-down transformers used for?
Used to decrease the potential difference from the transmission cables to the mains supple in buildings so it is safe to use.
What are the advantages of using overhead electrical cables?
- Cheaper to install.
- Easier to repair.
What are the disadvantages of using overhead electrical cables?
- Damaged by wind.
- Visual pollution.
What are the advantages of using underground electrical cables?
- No visual pollution.
- Not damaged by wind.
- No one gets electrocuted.
- Cannot be pulled out by people.
What are the disadvantages of using underground electrical cables?
- More expensive to install.
- Harder to repair.
What charge does an atom have and why?
No charge because it has an equal numbers of positive protons and negative electrons.
When can insulating materials become charged?
When they are rubbed with another insulating material because electrons are transferred from one material to another.
What happens if a charged object is placed in the electric field of another object?
It experiences electrostatic force and the 2 charged objects exert a non-contact force on each other.
What does a series circuit look like?
The components are connected one after the other in a single loop.
In a series circuit what happens if one component stops working?
The whole circuit stops working.
What does a parallel circuit look like?
Made up of 2 or more loops.
What happens in a parallel circuit if one branch stops working?
The other branches will not be affected.
What are the rules of a series circuit?
- Resistance is added together.
- Current is the same everywhere.
- Voltage is shared.
What are the rules of a parallel circuit?
- The resistance gets lower the more resistors you add and is never higher than the lowest resistor value.
- The current is shared.
- The voltage is the same everywhere.
What is Ohms law?
The current through a component depends on the resistance and the potential difference. The greater the resistance of the component, the smaller the current for a given potential difference.
What is resistance?
A measure of how difficult it is for current to flow through a resistor.
What happens to the current in an electrical circuit if the resistance is increased?
The current decreases.
What happens to the current in an electrical circuit if the potential difference is increased?
The current will also increase.
What is current?
The movement of electrons.
What is an electrical insulator?
A material that doesn’t allow the flow of electric charges/currents to pass through it.
what is a conductor?
A material that allows electric currents to pass through it.
what is potential difference?
A measure of how much energy is transferred between 2 points in a circuit.
