The discussion revolves around a past paper electricity problem from the AS physics syllabus, specifically focusing on applying Kirchhoff's laws to analyze a circuit with missing data.
The discussion is active, with participants exploring different interpretations of the circuit setup. Some guidance has been offered regarding the calculation of voltage drops and the treatment of specific resistors in the analysis.
There are indications of missing information in the original question, which may affect the analysis. Participants are also considering the implications of simplifying assumptions, such as setting point P to zero volts.
Yes, and the question wants you to find that missing data. To start, what is the potential difference between P and R?Peter R said:
Ehhh I'm thinking 3V+6V+5V+SRNFuller said:
The two top resistors connect P and R, so the potential difference between P and R must be the sum of the difference across those two resistors.Peter R said:
Right so that leads to 4v on the bottom unknown resistor. Also shouldn't the middle resistor be taking into consideration when calculating the voltage across PR, or you can just ignore it in a question of this kind?NFuller said:
YesPeter R said:
The middle resistor is not dropping any voltage between P and R, so it is ignored at this point.Peter R said:
So what are you supposed to do after finding the 4V drop at the bottom?NFuller said:
You need the difference between Q and S. If you consider P to be at zero volts for simplicity, then it should be obvious what the voltage at Q is and what the voltage at S is.Peter R said:
