Modelling the Variation of Resistance with Illumination Light can cause a change in conductivity of some semi-conductors When light is absorbed by the material it causes more electrons to be availa...
Modelling the Variation of Resistance with Temperature All materials have some resistance to the flow of charge As free electrons move through a metal wire, they collide with ions which get in thei...
Core Practical 3: Investigating E.M.F. & Internal Resistance Aims of the Experiment The overall aim of the experiment is to investigate the relationship between e.m.f. and internal resistance b...
E.M.F. vs. Terminal Potential Difference Terminal Potential Difference The terminal potential difference (p.d.) is the potential difference across the terminals of a cell If there was no internal r...
Internal Resistance All power supplies have some resistance between their terminals This is called internal resistance (r) Internal resistance causes some electrical energy to be transformed...
Electromotive Force When charge passes through a power supply such as a battery, it gains electrical energy The electromotive force (e.m.f.) is defined as: The amount of chemical energy converted t...
Potential Dividers & Variable Resistance The Potentiometer A potentiometer is a single component which can act as a potential divider. It consists of a coil of wire with a sliding contact A var...
Potential Dividers The electrical voltages rule is defined as: The sum of the e.m.f.s in a closed circuit loop is equal to the sum of the potential differences around that loop Therefore, wh...
Potential Difference & Conductor Length Potential Difference A cell makes one end of the circuit positive and the other negative. This sets up a potential difference across the circuit The pote...
