L3: Electricity sources and the National Grid Flashcards
What makes current flow?
Voltage/ potential difference
What is alternating current?
Current flow consisting of charges that continually change direction. These oscillations usually occur at a set frequency.
What would the graph of alternating current look like?
It will go above and bellow 0V - in the UK from 230V to -230V
What is alternating voltage?
A continually oscillating current flow, which results in a potential difference across 2 points, continually oscillating between a positive and negative value.
What is direct current?
Current flow consisting of charges flowing in a single direction only.
Give an example of supplies that provide direct current
Batteries and cells
What does the graph of direct current look like?
A straight, horizontal line across the x axis
What value does direct current always stay at?
It always stays at a positive value
Where do electrons flow in a direct current?
In the same direction
What is Mains Electricity?
It is the electricity that is brought to peoples’ homes via the National Grid. It is the supply of alternating current that in the UK has a frequency of 50Hz and p.d. of 230V.
What is the National Grid?
The National Grid is a network of wires that transport the electricity generated in a power station to our homes.
What is a transformer?
A device that can alter the potential difference of a an alternating current.
Why do we use step-up transformers increase the potential difference
Because current and the potential difference or voltage are inversely proportional, meaning that you can lower the current by increasing the voltage, decreasing the amount of energy lost in the overhead wires
Why do we use step-down transformers to lower the potential difference
Because current and the potential difference or voltage are inversely proportional, meaning that by decreasing the voltage, you can increase the current, making sure that there is an appropriate amount of current flowing into our homes.
What is the word equation for power?
Power = Current * Voltage
