Under this subtopic,u must be able to
1.Define what is emf?? U can check yr txt book or reference book for the definition..
E.m.f= total energy supplied by a cell(battery)to move a unit of electrical charge through a complete circuit
2. Then one of the most important part, u must be able to differentiate between Potential Difference(voltage) and EMF…U must include the similarities & differences between the two..
I advise u guys to do a table comparison,
3. U must also b able to Explain internal resistance..If u took chemistry, its easier to understand the following explaination…
a battery, has an electrode & electrolyte( i.e the liquid) which are resistive in nature. Due to this it produces internal resistance.
4. and one of the most crucial part is to understand the experiment on how to determine e.m.f & internal resistance
…u’ve got to hafal the circuit diagram..pls refer yr txt / reference book
please read the whole experiment, then analyse the graph.
Your basic maths on straight line must be tip top..otherwise u’ll b having problem to determine emf (E) & internal resistance (r) from the graph of voltage vs current.
Basically the graph is based on this equation:
E=V + Ir ,
re arranging the equation u’ll get
V = - r I + E , Then compare it with
y = m x + c (recall a straight line equation in your maths)
OBSERVE THIS COMPARISON:axis y = V
gradient, m = - r ( internal resistance)
axis x = I
y-intercept, c = E ( emf)
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