A group of engineering students compare the power of three electrical vehicle (EV) rapid-charging stations A, B and C using this method:
- They connect each charging station to a standard high-capacity battery pack.
- They initiate charging and record data.
- They measure the energy transferred to each battery pack every 40 s40\text{ s}40 s.
- They calculate the change in stored chemical energy of the battery packs.
a.[1]
Each charging station has the same efficiency and is used for the same length of time.
Describe one other factor the students should control in their method to make it a fair test.
b.[5]
The students test the charging stations using a valid method.
The graph below shows how the energy transferred to the battery pack varies with time for each charger:
Each charging station has the same efficiency.
Use data from the graph to:
- Describe in detail how the energy transferred varies with time.
- Compare the power of the three chargers, including calculations of their power.
c.[3]
How is electrical energy transferred from the main power station to the local distribution substations that supply these charging stations?
In your answer, write about:
- How electricity is distributed across the country.
- The type of voltage/current used.