IV graphs Flashcards
What are the IV graphs?
show how current varies as pd is increased
What graphs do we have to know about?
- metallic conductors (wires)
- filament lamps
- LDR
- thermistor
What does a graph look like for a metallic conductor?
why?
straight line through the origin
as it is an ohmic conductor and hence resistance stays constant, given temperature is aswell
What does an IV graph look like for a filament lamp?
S, but shallower
it starts steep but gets shallower as pd rises
this is because the filament lamp is coiled up lengths of metallic conductors, due to the heating effect
What does an IV graph look like for an NTC thermistor?
steep - shallow - steep
What is an NTC thermistor?
Negative temperature coefficient
the resistance decreases with temperature
What does a graph for an LDR look like?
The same as a thermistor, these are both semiconductors
What does the graph for a diode look like?
Nothing on the negative voltage, then at thershold positive voltage it spikes up, rises exponentially
What is on the y and x axis?
y = current x = pd
What circuit can we use to investigate IV ?
One with a power supply, an ammeter ,variable resistor and tested component in series, with a voltmeter in parallel to component..
