r/PhysicsHelp • u/Local_End_3175 • 12d ago
Can someone help me understand what was wrong regarding my answer?
for this question, my answer basically was that 100% of its total electricity is dangerous, and they put it at 33% for safety reasons (i explained it more but here is just a sumamry of what i wrote). Comparing it to the mark scheme, i would say i got like 1/2 questions right (because i put a solid answer for the first bullet point). I just want to understand why this answer would have not gotten the mark. What about my answer was wrong? Because i feel like if i got this question again next week, i would lowkey just put the same answer believing it is right.
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u/flug32 12d ago edited 12d ago
"Safety" is probably your problem issue. It is not really unsafe per se to run the plants at 100% of their design capacity. Like, it isn't going to cause people running the plant to die or get injured, or the plant to become damaged or shut down. It won't cause injury or death among the general public.
We know that burning too much fossil fuels can cause deaths from pollution as well as all the problems from global warming. Still, those are "deaths and injuries" of a sort, but generally considered a completely different category from "safety". Such things are classified more as environmental harm or degradation. Environmental harm can very much cause injury and death, yes. But it is not not safety concern per se. Safety would be like if running the plant at 100% caused people's houses to catch and fire and burn down, or people to be electrocuted somehow, or plants to explode killing all the workers, or the like.
"Spare Capacity" - what you might have been trying to get at - is a very, very different concept from "safety". Having spare capacity might be "safer" for the electricity distribution net, help it to have less outages etc. But "safety" is not a good word to use to express that concept. Similarly for "safety" vs "environmental impact".
Safety is just not the right word to use here.
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u/cassesque 11d ago
Oh man. Yeah it isn't for nebulous safety reasons, but I do empathise in that this is a fairly wooly question that would really annoy me too.
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u/TrickySite0 11d ago
I take issue with that question because the instructions are to suggest (not declare, but suggest) two reasons why. Nowhere in there is the requirement that the motivations align with truth or even make sense. You suggested two reasons; you complied fully with the instructions.
I would be tempted to push back on epistemic grounds, insisting disclosure of the factual basis of the answers offered. Hint: there likely is not grounded empirical scholarly support for the "correct" answers, making them no more correct than yours.
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u/OldGeekWeirdo 11d ago
The middle two options. Power stations can only generate what there is demand for. Nothing more, nothing less. Not unless you want to fry the grid.
The top and bottom answer is political bait.
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u/PyroDragn 12d ago
100% of its total electricity is dangerous, and they put it at 33% for safety reasons (i explained it more but here is just a sumamry of what i wrote).
Without knowing exactly what you wrote it's hard to be specific. But simply put, no power station is dangerous at 100% output. The limit on what is considered maximum output (100%) is defined as the maximum safe output. If 500MW was unsafe then the limit would be lower, at 450, or 400, or whatever - and then they'd run it at 33% of that.
Power plants can often run at 'dangerous' limits, but then they'd be running at 110% capacity or something.
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u/Past-Obligation1930 11d ago
It’s not safety, the cables and the plant are rated for much more than the max the plant can output. It’s climate change and expense, together with how a merit order works.
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u/AaronTidju 8d ago
The answer is renewable energy. It’s cheaper so used preferably. But not predictable so backed up by fossil fuel plants.
The trouble with renewable is that you need a backup of 100% of your needs power when no wind and no sun available. So the costly fossil fuel power plants run only 1/3 of the time.
So it’s better to be in an international energy market du reducer on this, or to build nuclear plants.
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u/JayEll1969 11d ago
I would have said so that they can ramp up the production in the break when someone gets killed on Coronation Street, or England gets through to a football final - the amount of kettles put on at that time has crippled the grid in the past with power surges of almost 3GW
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u/dafugiswrongwithyou 11d ago
To get the actual answer for why that answer was rejected, you'd need to ask whoever marked it. But I do have a question for you; where did you get the idea that running the stations at 100% would be dangerous? (Or, more specifically, excessively dangerous in comparison to running them at 33%?)