Exam Questions 203 Practice questions 206 Practical 206 Practical PaperworkRevision Material Generator and Motor calculations Additional Revision 
So what is Resistance? Resistance is defined as the ability of a substance to prevent or resist the flow of electrical current. A substance resists electrical current because of a collision between electrons and atoms, which slows the electrons down and converts some of their energy to heat energy. In some cases, the energy is also converted into light. So how can I calculate Resistance? To calculate resistance using the formula below you will need to know three things. You will need to know the Resistivity of the material you are using. The Length of the material you are using, and the cross sectional area. once you have these three things you can begin to find resistance. Below I will give an example so you are able to see how given specific units you are able to calculate resistance. Example Question: A length of copper is 125m long, having an area of 2.0mm2 has a specific resistance of 1.67x108. What is the resistance?
