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
Electricity in the home
2 types of electricity supplies = alternating current (ac) and direct current (dc).
- AC supplies = current is constantly changing direction = produced by alternating voltages (positive and negative ends keep alternating)
- UK main supply is an AC supply = 230V
- Frequency of AC mains supply = 50 Hz
- Cells and batteries supply DC = current that is flowing in the same direction
- Most electrical appliances connected to mains supply by three-core cables= they have three wires inside, each with a core of copper and a coloured plastic coating.
- Colour of insulation = shows purpose = colours the same for every appliance = easy to tell apart the wires
- Live wire = brown . It provides the alternating potential difference (at about 230V)
- Neutral wire = blue. It completes the circuit and carries away current. Electricity usually flows in through the live wire and out through the neutral wire. It is around 0V
- Earth wire = green and yellow. It is for protecting the wiring and for safety. It stops the appliance becoming live. It doesn’t usually carry a current (only if there is a fault). It is also at 0V .
- Our bodies are at 0V = if you touch the live wire = large potential difference produced across body = current flows through you = causes a large electric shock = risk of injury or death
- Even if plug socket or switch is turned off = still a danger of electric shock. Current is not flowing but there is still potential difference in the live wire. Contact with the live wire = body provides a link between supply and earth = current would flow through you.
- Any connection between the live wire and earth = dangerous. If the link creates a low resistance path to earth = huge current will flow = fire.
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……?’