I/V Characteristics Flashcards
What does the I/V characteristic graph for a metallic conductor look like
Exactly the same as one for a ohmic conductor
The shallower the gradient of a characteristic I/V graph, the …. The resistance of the component
Greater
What does the I/V characteristic graph for a filament lamp look like
Curve
Starts STEEP gets SHALLOWER as voltage rises
What does a filament lamp not have the same characteristic graph as a metallic conductor as the lamp is a coiled-up length of metal wire
Because the CURRENT flowing through the lamp increases it’s TEMPERATURE
The RESISTANCE of a metal increases as the TEMPERATURE increases
What are semi conductors used in
Sensors
Why are semiconductors nowhere near as good at conducting electricity as metals
They have fewer CHARGED CARRIERS available
What makes semiconductors excellent sensors for changes in the environment
If ENERGY is SUPPLIED to the semiconductor
More CHARGE CARRIERS can be released
Name three semiconductors
Thermistors
LDRs
Diodes
What is a thermistor
A RESISTOR that depends on TEMPERATURE
What does the NTC thermistor stand for
Negative Temperature Coefficient
What does negative temperature coefficient mean
The RESISTANCE decreases as the TEMPERATURE goes up
What does the characteristic graph for a thermistor show
Curves upwards
Starts shallower gets sleeper
Explain in terms of temperature and current why the resistance decreases
Increasing the CURRENT through a thermistor increases it’s TEMPERATURE
The increasing GRADIENT of this characteristic graph tells you that the RESISTANCE is decreasing
Explain why warming the thermistor makes the resistance lower
Gives more ELECTRONS enough ENERGY to ESCAPE from their atoms
This means more CHARGE CARRIERS available
What does the resistance of an LDR depend on
Light intensity
