Questions about Electricity

Electricity and magnetism: current, voltage (potential difference), charge, resistance; relationships between them and links to energy and power. Elementary circuits including batteries, wires, resistors, filament lamps, diodes, capacitors, light dependent resistors and thermistors; series and parallel circuits. Elementary electrostatic forces and magnetism; electromagnets, motors and generators. Current as a flow of electrons; thermionic emission and energy of accelerated electron beams.

Quite a few of the questions in the PAT involve capacitors, which you probably won’t have covered at AS level, so it is important that you learn about capacitors and especially simple RC circuits and time constants.  If you are doing Further Maths you might be interested to look at some material about AC circuits and impedance, but you only really need to learn about DC to do the PAT questions.

Answers to electricity questions

2010, question 13

2010, question 18

2011, question 17

2011, question 18

2012, question 18

2013, question 11

2013, question 13

2014, question 13

2014, question 16

2015, question 21

6 thoughts on “Questions about Electricity

    1. Hi — that’s a good question. I think that it would be a good idea to know and understand the equations relating to series and parallel capacitors. They just result from applying the law Q = VC and they are not too hard to understand, but mastering them should give you some insight into how capacitors work — I think a good resource for this is http://tap.iop.org/electricity/capacitors/127/page_46171.html, whih includes derivations of both series and parallel resistor equations.

  1. Hi, thanks for your efforts in putting this valuable resource together. I was wondering if you could point me to any previous questions on EM induction (that aren’t to do with transformers, since this topic is no longer on the syllabus) and magnetism?

    1. Just to recap, magnetism only comes up in the syllabus here: ‘(Elementary electrostatic forces and) magnetism; electromagnets, motors, generators.’ This sentence used to finish with ‘and transformers’, but this was deleted a couple of years ago.

      I’m afraid I can’t think of any questions that have come up on this subject. I assume that all you need to know is the basic idea and the left- and right-hand rules, but the syllabus is a bit vague and in the absence of previous questions there really isn’t much to go on here.

    1. I haven’t found a particularly good source on the web. But if you search for ‘electron beam energy thermionic emission “a level”‘, there are some fairly good links.

      The essential points to remember are that:
      1. When you heat a metal wire hot enough, some electrons gather enough energy that they escape the solid metal — that is thermionic emission.
      2. If you accelerate an electron (with charge e) across a potential difference of V, the electron acquires a kinetic energy of eV. And by considering the formula for kinetic energy, this means that (if it starts with zero speed) the electron will be accelerated to sqrt(2eV/m).

      And that’s all you need to know about the topic to do well in the PAT exam.

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