1. The problem statement, all variables and given/known data Using the diagram for the I-V characteristic of a semi-conductor (attached). Answer the following questions: 1. Why is the resistance of an I-V characteristic not determined by the gradient of the graph 2. Explain why the temperature of semiconductor increases 3. Explain why the resistivity goes down. I am mainly stuck with question 2. 2. Relevant equations p = RA/l (p = resistivity, R = resistance, A = area, I = length. P= I^2 R 3. The attempt at a solution 1. I don't know whether they are trying to get at - is it because it is the inverse as it is current versus voltage or is it that the gradient is the rate of change which would be wrong as resistance is just the ratio of voltage to current (i.e. if its a curve you would not take the tangent)? 2. This is the bit I am stuck with. I checked the answer and it says that you must use P = I^2 R to justify the increase in temperature and cannot justify it in terms of voltage increase. This is what confuses me. The graph shows the voltage increases and voltage is proportional to power, so I don't understand why you must use P = I^ R? 3. Resistivity goes down because area and length are constant but resistance goes down so therefore resistivity must go down. Many thanks for any help.