Table of Contents
Week 1 | KS3 Physics
Week 2 | KS3 Physics
Week 3 | KS3 Physics
Week 4| KS3 Physics
Week 5| KS3 Physics
Week 6| KS3 Physics
Week 7| KS3 Physics
The National Grid
- National Grid = giant system of cables and transformers that covers UK and connects power stations to consumers, which are using electricity
- Transfers electrical power from power stations (supply) to anywhere on the grid where it is needed (demand)
- Electricity demand changes throughout the day = power stations must produce enough electricity to meet these demands
- Can predict when most electricity will be used: in the morning, coming home from school/work, when it starts to get dark/cold and popular TV events (sports)
- There is spare capacity for power stations to cope with the high demand as they work below their max power output
- Smaller stations can start up in case of emergencies
- To transmit huge amount of power = need either a high potential difference or a high current
- But with high current = lose lots of energy as wires heat up and energy is transferred to thermal energy store of surroundings
- Cheaper to increase the potential difference (400,000V) and keep current low as possible.
- Increasing potential difference = decreases current = decreases energy lost by heating the wires and surroundings = national grid efficient way of energy transfer.
- To get potential difference very high it requires transformers, big pylons with huge insulators
- Transformers step up the potential difference at one end for efficient transmission then bring it back down to a safe level at the other end .
- Potential difference is increased at STEP UP TRANSFORMER
- Potential difference is reduced at STEP DOWN TRANSFORMER
How long have you…? (present perfect 4) Exercises
Use the information given to create questions beginning with ‘How long…?’
• It is snowing.
• The weather is shining.
• John and Kate are married.
• My brother has gone on holiday.
• My aunty and uncle live in Canada.
• My sister is a teacher.
• I work at the chemist.
• I’ve known Susan since I was a baby.
• Jonathan is learning to speak to Mandarin.
Fill in the missing gaps in the sentences using the present perfect (=has/have + past participle)
• I have known Kate a long time.
• My brother has been playing the piano he was 11 years old.
• My mum and dad on holiday to America. They
gone since last Sunday.
• I Ben and Emma since primary school.
We to the same primary and secondary school.
• My sister learning to speak French because she
is going to France next month.
have you lived lives to
has been works have known
I have bought have worked.
• My sister in Spain. She is studying Spanish
with her friend Rosie. I Rosie since I was 5.
• Spencer like with Jamie. They have worked
together for 2 years.
• How long in Australia?
• a new dress for prom.
• He to Thorpe park.
Challenge: Create 4 of your own questions beginning with ‘How long……?’