O/A Level Physics Simplified

Last minute revision tips for Physics UNIT 2
ELECTRICITY
● Always construct answers involving potential divider from the context of voltage, not current!
● Questions involving resistance and dimensions of a material should always be answered using the intrinsic equation of resistance (R=ρl/A)
● The y intercept gives the emf and the negative of the gradient gives the internal resistance for the V-I graph
● In a series circuit, the higher the resistance of a component, the greater the P.D across that component
● To answer questions that ask why the resistance of certain materials (metals/ thermistors) change with temperature, always use the transport equation, I = nAve
● While analysing graphs of electricity, make sure you have assessed the axes carefully i.e whether it's a V-I graph or an I-V graph
● If identical resistors are connected in parallel, the total resistance given by an individual resistance divided by number of resistors. for example, if three 9 Ohm resistors are connected in parallel, the total resistance is 9/3 = 3 Ohm!
● If two cells are connected + to - , the resultant emf is the summation of the two emfs. If two cells are connected + to +, the resultant emf is given by the difference between the two emfs
● Some questions will try to trick you into opting for a wrong method. Always try to link a question with either the definition or the equation. For instance, if a question asks you to find the rate at which energy is being transferred, it's basically asking you to find the power!
● While calculating values using gradient from graphs, always remember to draw a tangent if it's a curved line! Local values don't give the gradient if it's a curved line.