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# I- watch

1. Sorry the TSR website glitched out the title is supposed to say "I-V Diode Circuit Question"

Attachment 728350728352
The mark scheme:
Attachment 728350728352728300

What I don't get is why they're so wildly different, what is the curly arrow mean? Why does their circuit have a resistor on it?
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2. They've drawn that to indicate a variable voltage supply - the 'curly arrow' and resisltor are being used as a potential divider.

To make your circuit complete, you also need to add something to show you are varying the voltage supplied - either the double cell symbol with the arrow through it, or alternatively add a variable resistor in the main part of the circuit (ie beside the cell).

If you can't vary the voltage, you can't produce a graph.
3. (Original post by Retsek)
Sorry the TSR website glitched out the title is supposed to say "I-V Diode Circuit Question"

Attachment 728350728352
The mark scheme:
Attachment 728350728352728300

What I don't get is why they're so wildly different, what is the curly arrow mean? Why does their circuit have a resistor on it?

The whole setup is also known as a potentiometer.

The “curly arrow” represents the movable jockey.

I would not encourage that you use a variable resistor that is connected in series to the power supply and diode. There is a subtle point to this setup because it does not always produce the required I-V graph of a diode -the setup does not give the full range of the required voltages. (A question that I would set to ask students to test their understanding.)

The setup given in the MS would definitely give the full range of the required voltages.

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Updated: March 2, 2018
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