Electricity in the home



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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


 

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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.

 

 

Use the appropriate words in the missing gaps.

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……?’

1.

2.

3.

4.

 

 

 

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“Every accomplishment starts 
With the decision to try.” Gail Dever

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