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P2: Quiz 14 – Answers
P2: Quiz 14 – Answers
1) produced, needed/ used
The National Grid takes energy from where it has been PRODUCED to anywhere that it is NEEDED/ USED
2) Power = current x potential difference, or P = IV
Power is measured in watts (W), current is measured in amps (A) and potential difference is measured in volts (V)
3) The national grid transports electricity by having a very high potential difference (400,000 V) and a low current. By having a high PD and a low current, the wires and the surroundings heat up less, which means that less energy is lost when transporting the electricity. (A high current would result a lot of energy being transferred to the thermal energy stores of the wire and the surroundings; lots of energy is lost)
4)
a) A step-up transformer increases the potential difference and decreases the current
b) A step-down transformer decreases the potential difference and increases the current
5)
a) Primary coil
b) Secondary coil
c) Iron
6)
a) 30 V
b) The transformer is a step-down transformer as the potential difference decreases; the potential difference across the primary coil is 240 V and the potential difference across the secondary coil is 30 V. (Also, the current increases; the current through the primary coil was 0.5 A, and the current through the secondary coil is 4 A)
7)
a) 0.3125 A
b) The transformer is a step-up transformer as the potential difference increases; the potential difference across the primary coil is 25,000 V and the potential difference across the secondary coil is 400,000 V. (Also, the current decreases; the current through the primary coil was 5 A, and the current through the secondary coil is 0.3125 A)
8) 12,000 V
The National Grid takes energy from where it has been PRODUCED to anywhere that it is NEEDED/ USED
2) Power = current x potential difference, or P = IV
Power is measured in watts (W), current is measured in amps (A) and potential difference is measured in volts (V)
3) The national grid transports electricity by having a very high potential difference (400,000 V) and a low current. By having a high PD and a low current, the wires and the surroundings heat up less, which means that less energy is lost when transporting the electricity. (A high current would result a lot of energy being transferred to the thermal energy stores of the wire and the surroundings; lots of energy is lost)
4)
a) A step-up transformer increases the potential difference and decreases the current
b) A step-down transformer decreases the potential difference and increases the current
5)
a) Primary coil
b) Secondary coil
c) Iron
6)
a) 30 V
b) The transformer is a step-down transformer as the potential difference decreases; the potential difference across the primary coil is 240 V and the potential difference across the secondary coil is 30 V. (Also, the current increases; the current through the primary coil was 0.5 A, and the current through the secondary coil is 4 A)
7)
a) 0.3125 A
b) The transformer is a step-up transformer as the potential difference increases; the potential difference across the primary coil is 25,000 V and the potential difference across the secondary coil is 400,000 V. (Also, the current decreases; the current through the primary coil was 5 A, and the current through the secondary coil is 0.3125 A)
8) 12,000 V
Questions
1) Fill in the gaps in the sentence below.
The National Grid takes energy from where it has been _______ to anywhere that it is _______
2) Write down the equation that links potential difference, power and current. Give the units for each of the values as well.
3) In the National Grid, electricity travels along power line; describe the potential difference and current of the electricity as it travels along these power lines. Explain why the electricity has this potential difference and current.
4) There are two different types of transformers; a step-up transformer and a step-down transformer.
a) Describe what happens to the current and potential difference at a step-up transformer.
b) Describe what happens to the current and potential difference at a step-down transformer.
5) The diagram below shows what a transformer looks like.
1) Fill in the gaps in the sentence below.
The National Grid takes energy from where it has been _______ to anywhere that it is _______
2) Write down the equation that links potential difference, power and current. Give the units for each of the values as well.
3) In the National Grid, electricity travels along power line; describe the potential difference and current of the electricity as it travels along these power lines. Explain why the electricity has this potential difference and current.
4) There are two different types of transformers; a step-up transformer and a step-down transformer.
a) Describe what happens to the current and potential difference at a step-up transformer.
b) Describe what happens to the current and potential difference at a step-down transformer.
5) The diagram below shows what a transformer looks like.
a) For the above transformer, what is the name of the coil on the left?
b) For the above transformer, what is the name of the coil on the right?
c) What is the core of transformers made from?
The remaining questions in this quiz will use the equation below.
b) For the above transformer, what is the name of the coil on the right?
c) What is the core of transformers made from?
The remaining questions in this quiz will use the equation below.
6) The primary coil in a transformer has a potential difference of 240 V and a current of 0.5 A. The current in the secondary coil is 4 A.
a) Calculate the potential difference across the secondary coil.
b) Is the transformer a step-up or a step-down transformer. Explain your answer.
7) The primary coil in a transformer has a potential difference of 25,000 V and a current of 5 A. The potential difference in the secondary coil is 400,000 V.
a) Calculate the current in the secondary coil. Do not round your answer.
b) Is the transformer a step-up or a step-down transformer. Explain your answer.
8) The primary coil in a transformer has a current of 200 A and an unknown potential difference. The secondary coil in a transformer has a potential difference of 400,000 V and a current of 6 A. Calculate the potential difference in the primary coil.
a) Calculate the potential difference across the secondary coil.
b) Is the transformer a step-up or a step-down transformer. Explain your answer.
7) The primary coil in a transformer has a potential difference of 25,000 V and a current of 5 A. The potential difference in the secondary coil is 400,000 V.
a) Calculate the current in the secondary coil. Do not round your answer.
b) Is the transformer a step-up or a step-down transformer. Explain your answer.
8) The primary coil in a transformer has a current of 200 A and an unknown potential difference. The secondary coil in a transformer has a potential difference of 400,000 V and a current of 6 A. Calculate the potential difference in the primary coil.