3.5.1.2 - Current-Voltage Characteristics Flashcards
What is an ohmic conductor?
The current is directly proportional to the potential difference.
When does an ohmic conductor produce a straight line on a graph of I against V?
When the physical conditions, such as temperature remain constant.
What is the circuit symbol for a variable resistor?
A rectangle with an arrow pointing towards the right hand corner through the rectangle.
Describe the two graphs for an ohmic conductor?
Both straight lines through the origin, however the V/I graph is shallower.
Describe the two graphs for a filament lamp.
I/V is the shape of an s, through the origin.
V/I opposite to I/V graph, curves upwards once past the origin.
What happens to the resistance in metal filament?
Increases as the temperature increases. This is because ions in the metal filament vibrate more as the temperature increases, resisting the passage of electrons to a greater extent.
What is the filament lamp an example of?
A non-ohmic conductor.
Why aren’t semiconductors as good at conducting electricity?
There are far fewer charger carriers available.
When and why are more charge carriers released to semiconductors.
If energy is supplied to the semiconductors, more charge carriers can be released. This means they make excellent sensors for detecting changes in their environment.
What are the two types of semi conductors?
Thermistors and diodes.
What is a thermistor?
A resistor with a resistance that depends on its temperature.
What happens as resistance is increased in a NTC thermistor?
The resistance decreases as the temperature goes up.
Describe the two graphs for a thermistor?
The I/V graph is a reverse of an s. After the origin it curves upwards.
The V/I graph is shaped like an s.
What happens when you warm a thermistor?
It gives more electrons enough energy to escape from their atoms. This means that there are more charge carriers available, so the resistance is lower.
Describe the symbol of a thermistor.
Rectangle with a horizontal line underneath which then crossed through the rectangle towards the right hand corner.
