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Explain the advantage of transmitting electricity at a very high potential difference - AQA - GCSE Physics - Question 10 - 2021 - Paper 1
Question 10
Explain the advantage of transmitting electricity at a very high potential difference. 1. High potential difference leads to very low currents. 2. Lower currents re... show full transcript
Worked Solution & Example Answer:Explain the advantage of transmitting electricity at a very high potential difference - AQA - GCSE Physics - Question 10 - 2021 - Paper 1
Step 1
Explain the advantage of transmitting electricity at a very high potential difference.
Answer
Transmitting electricity at very high potential differences has several advantages:
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Low Current Flow: A high potential difference results in a lower current for the same power transmission. This is expressed by the formula:
where is power, is voltage (potential difference), and is current. For a constant power, increasing the voltage allows for a proportionate decrease in current.
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Reduced Energy Loss: The reduced current flow minimizes the amount of thermal energy dissipated as heat in the cables. Less energy lost in this manner leads to greater efficiency in power transmission.
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Increased Transmission Efficiency: Overall, the use of high potential differences increases the efficiency of power transmission, allowing for more electricity to reach its destination effectively.
Step 2
It is dangerous for a person to fly a kite near an overhead power cable.
Answer
A person flying a kite near an overhead power cable is at risk of receiving a fatal electric shock because:
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Electric Field Strength: The electric field strength near high-voltage cables is very high. This can ionize the surrounding air, allowing it to become conductive.
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Kite Conducting Charge: If the kite or string gets too close to the power cable, the charged particles may flow to the person holding the kite, leading to a potentially fatal shock.
Step 3
Draw a line on Figure 15 to show how the potential difference changes with distance if the humidity of air increases.
Answer
When humidity increases, the air becomes a better conductor of electricity. Therefore, the potential difference required to maintain conduction will be lower at any given distance. To represent this on Figure 15, draw a line below the original line, starting from the origin and curving upwards to the right, showing less potential difference required at each distance with increased humidity.
Step 4
Explain why the current in the steel wire is different from the current in a single aluminium wire.
Answer
The current in the steel wire differs from the current in a single aluminium wire due to their relative resistances:
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Resistances in Parallel: The individual wires (aluminium and steel) act as resistors in parallel. The overall resistance of parallel resistors is lower than that of the individual resistors.
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Higher Resistance of Steel: Given that the resistance of the steel wire is greater, according to Ohm's Law (
where is voltage, is current, and is resistance), for a constant voltage, this means that the current flowing through the steel wire will be less than that through the single aluminium wire. Hence, the aluminium wire being a better conductor allows for a higher current to flow.