16540494
| Question | Answer |
| What is Ohm's law? | Current in a conductor is proportional to the p.d across it, providing the temperature is kept constant (I ∝ V) V = I x R |
| What is an Ohmic conductor? | A material / conductor which obeys Ohm's law |
| IV graph for an Ohmic material (e.g. resistor) : | |
| Why is the IV graph for a Ohmic material like this? | Ohm's law is obeyed, so I ∝ V Under constant physical conditions (e.g. temperature) |
| IV graph for filament lamp : |
Image:
5dg9x (image/gif)
|
| Why is the IV graph for a filament lamp shaped like this? | Ohm's law not obeyed As V increases, I increases As I increases, Temperature increases As temperature increases, R increases (therefore not straight line) |
| How would we find the resistance using an IV graph for an Ohmic conductor? | Find gradient (this works as we can rearrange V=IR to I=RV and say I=1/R x V. This is the same as y=mx+c as our intercept for I=1/R x V is 0, so I=1/R x V + 0 ) |
| How would we find the resistance using an IV graph for an filament lamp? | Use values from the graph: Vx/Ix = Rx |
| IV graph for diode (aka semi-conductor) : |
Image:
V I Diode (image/png)
|
| Why is the IV graph for a diode shaped like this? | Non-Ohmic If current is the wrong way (reverse bias) then resistance is really high so current is therefore tiny |
| What is forward bias? | The direction current is able to flow |
| What is threshold voltage and what is the value of threshold voltage for a diode? | A minimum voltage needed to allow current to flow through and the value for a diode is 0.6V |
| What kind of diodes have a higher threshold voltage than normal diodes? | LED's |
| What are the threshold voltages for : Diodes LED's | Diodes = 0.6 V LED's = 1.5 V |
| On IV graphs, how do we get negative readings on the graph? | Reverse the direction of the battery |
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