Archive for category Physics

Physics Assumed Knowledge

The following is a (not necessarily complete) list of assumed knowledge for Physics in GAMSAT. It’s everything I’ve come across from taking the practice papers and the real exam (London 2009). Learn it all and you’ll probably do well.

  • Kinematics (solving simple problems with kinematic equations)
  • Optics (lenses, focal length, mirrors, shadows)
  • Currents and circuits (parallel and serial circuits, resistors, cells, possibly capacitors)
  • The inverse square law (its applications in electrical, magnetic and gravitational fields)

Introduction to parallel and series circuits

A common question in Gamsat is to estimate the current flowing in a portion of an electrical circuit.

The video below (not embeddable) is a good introduction to parallel and serial circuits

http://www.youtube.com/watch?v=E8AZBR8Zz04

Ohms Law

Current = Voltage / Resistance

Currents in Parallel and Series Circuits

To calculate the current flowing across each globe, for each circuit:

  1. Calculate the total resistance by reducing the circuit using ohms law.
  2. Resistors in series will all have the same current flowing through them.
  3. Resistor in parallel will have a portion of the current flowing through them, so if there are 3 resistors in parallel and they are all the same then each will have 1/3 of the total current flowing through it.

Inverse Square Law

  1. The inverse square law applies to gravity and magnetic charges.
  2. force = sum of charges / distance2