21.3 Paying for Electricity and National Grid Flashcards
Why is electrical energy so useful?
Electricity is very useful to us as electrical energy can be easily transferred into other types of energy.
What does the amount of electrical energy transferred by a device depend on?
The amount of electrical energy a device transfers depends on how long the appliance is switched on and it’s power.
Define the power of an electrical device.
The power of an electrical device is how quickly it transfers energy.
It is measured in watts (W) or kilowatts (kW).
Define the kilowatt-hour - kWh.
One kilowatt-hour is the amount of energy transferred when one kW is left on for one hour.
What is the national grid?
Cables.
Pylons.
Transformers.
What is the purpose of transformers in the National Grid?
Step-up transformers increase and step-down transformers decrease the voltage of mains electricity.
Why do we step-up voltage in the national grid?
High voltage (up to 500,000V) in power lines reduces current. Low current reduces energy losses in the cables.
What is the advantage and disadvantage of underground power cables?
Advantage - not damaged by storms and are not unsightly.
Disadvantage - Expensive and take long time to repair.
