Oxford PAT 2011, Questions 17 – 21

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5 thoughts on “Oxford PAT 2011, Questions 17 – 21

  1. Hi, for number 18 what topic should I study for this? I have reviewed electricity etc. but have not seen such anywhere? Is this related to motors and generators?

    P.S: Are time constants on the exam alot?

    1. Hi Jacob, that’s a good question. I think that possibly it may have been a mistake by the examiners to set question 18: if you look at the examiners’ report for 2011 it refers to a part of one question that was off the syllabus. However, transformers could at a pinch be considered to be part of the ‘electromagnets’ topic, so it’s maybe worth having a quick read of a basic tutorial on transformers like http://www.learnabout-electronics.org/ac_theory/transformers01.php.

      By time constants, you mean RC circuits? If so, it is worth being familiar with how the capacitor law Q = VC, and Ohm’s law V = R dQ/dt lead to the differential charge/discharge equation Q = (-) RC dQ/dt, and how to solve this to get an exponential decay.

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