2006 question 3 - faulty IRJ

[BedfordBoy]

In my day Ohm's law Kirchoff's law and algebraic equations were school physics, but yes, these are what you want to use.

Thanks, this solution is a lot simpler than I was making it. The crucial step I was missing was calculating the voltage drop across the feed resistor and hence the supply current. As for high school physics, I'm sure you're right but I'm afraid I have even less chance of remembering that than I do university physics. I seem to recall dropping a cricket ball and a marble off a balcony...