The National Grid Flashcards
Electricity (18 cards)
What is the national grid?
A giant system of cables and transformers that covers the UK and connects power stations to consumers.
What does the national grid transfer?
Electrical power from power stations (the supply) to where it is needed (the demand).
Why must electricity production meet demand?
Electricity usage changes throughout the day, and power stations must produce enough electricity for everyone to have it when needed.
When does demand for electricity typically increase?
- When people wake up in the morning
- When people come home from school or work
- When it gets dark or cold outside
- During popular events like a sporting final on TV
What do power stations do to manage unexpected demand?
Power stations often run well below their maximum power output to have spare capacity and keep smaller power stations on standby.
What is the advantage of using high potential difference (pd) in the national grid?
It allows for the transmission of huge amounts of power while keeping the current low, which reduces energy loss as heat.
What happens to energy when high current is used in power transmission?
Lots of energy is lost as the wires heat up and energy is transferred to the thermal energy store of the surroundings.
What voltage is used for efficient transmission in the national grid?
400,000 V.
What is the role of transformers in the national grid?
Transformers change the potential difference for efficient transmission.
What type of transformer is used to increase potential difference?
A step-up transformer.
How does a step-up transformer work?
It has more turns on the secondary coil than the primary coil, which increases the potential difference.
What happens to the current when the potential difference is increased by a transformer?
The current is decreased.
What type of transformer is used to decrease potential difference at the consumer end?
A step-down transformer.
How does a step-down transformer work?
It has more turns on the primary coil than the secondary coil, which decreases the potential difference and increases the current.
What is the formula for power in a transformer?
Power = potential difference (pd) X current.
Are transformers efficient?
Yes, transformers are nearly 100% efficient.
What relationship does power in the primary coil have with power in the secondary coil?
Power in the primary coil = Power in the secondary coil.
Fill in the blank: The power of a primary coil is given by _______.
power = pd X current.
