Electricity

#1
Would my circuit be correct?
Last edited by Student 999; 1 month ago
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1 month ago
#2
The circuit u drawn, the pd across the diode cannot be 0
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#3
(Original post by Ethanity007)
The circuit u drawn, the pd across the diode cannot be 0
Why would you need the pd across it to be zero? Isn't the point of the experiment to vary the pd across the diode and take readings of current and voltage?
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1 month ago
#4
U are supposed to get a graph in figure 1. One of the point is pd=0
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1 month ago
#5
The mark scheme says 'condone variable resistor' - so your answer would be accepted.
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#6
(Original post by Stonebridge)
The mark scheme says 'condone variable resistor' - so your answer would be accepted.
Just to check, is the idea of having a variable resistor to create a potential divider circuit that'll allow different voltages and current to be measured. Another question is this only works when the diode has resistance. If the diode had negligible resistance then it would act as a wire and would't have a pd across it?
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1 month ago
#7
(Original post by Student 999)
Just to check, is the idea of having a variable resistor to create a potential divider circuit that'll allow different voltages and current to be measured. Another question is this only works when the diode has resistance. If the diode had negligible resistance then it would act as a wire and would't have a pd across it?
The variable resistor is not a potential divider. The diagram in the answer sheet is a potential divider.
However, both circuits enable you to vary the current through the diode. So both were accepted.

The diode doesn't have zero or negligible resistance - this is what the graph shows. At point A on the graph its resistance R = V/I
If the diode had negligible resistance you would need a resistor (or variable resistor) in the circuit to limit the current.
The diode will always have a pd across it, even if that pd is very small.
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