# Science talk:Math Exam Resources/Courses/MATH152/April 2016/Question A 25

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Thread title | Replies | Last modified |
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Incorrect equation for I | 0 | 20:07, 26 March 2018 |

Incorrect Hint and Solution | 4 | 03:03, 19 March 2018 |

Hi Aili and Brian,

There was an error in Aili's solution: the current entering the top node is I + i_1 and the current leaving the top node is i_2, so we get I = i_2 - i_1. A circuit very similar to this one also appears in the following problem:

http://wiki.ubc.ca/Science:Math_Exam_Resources/Courses/MATH152/April_2017/Question_B_03_(a)

Hello Aili,

For Kirchhoff's circuit laws, we need to take into account both the circuits and the voltages (encoded as linear equations). For the voltage portion of Kirchoff's laws, resistors are also included as voltage = current x resistance.

Thanks,

Brian

MATH152/April 2016/Question A 25

Actually, you are correct (and the hint looks good). However, it may be helpful for students if you made your solution more clear (for instance, applying Kirchoff's circuit laws to which node of the diagram).

Thanks,

Brian

Hey Brian,

This one is based on the notes http://www.math.ubc.ca/~elyse/152/2018/5Circuits.pdf

Again, I am not an expert on such questions though I tried to spend some time going through the lecture notes online and learn it, so please feel free to add more details to the solutions.

For this question, I think it only asks **one linear equation that matches the loop currents to the current source**, so I am not sure whether we should consider the resistor * current= voltage equation.

Thanks. Aili