I-V Characteristics Flashcards
I-V Graphs shows how […….] varies
Resistance
What is the circuit called that you use to investigate I-V characteristics of a component?
Test circuit
In a test circuit what do you use the variable resistor for?
To alter the Potential Difference and the current flowing through it
In a test circuit why do you repeat your measurements?
To take averages and to reduce the effect of random errors on your results
For the current through an ohmic conductor to be directly proportional to the Potential Difference what must remain constant?
The temperature
For an ohmic resistor what does a shallow gradient mean?
The conductor has a greater resistance
What is the I-V characteristic for a Filament Lamp?
The graph is curved
What happens to the curve of a filament lamp as Potential Difference rises?
The curve starts to get SHALLOWER (less steep gradient)
The resistivity of a metal increases with [………]
Temperature
How is charge carried through metals?
By free electrons in a lattice of positive ions
Explain how the resistivity of a metal increases with temperature.
- Charge is carried through metals by free electrons in a lattice of positive ions
- Heating up a metal makes the lattice ions vibrate more, meaning electrons collide with them more frequently, reducing their drift velocity and transferring some of their kinetic energy into other forms
- When they lose KE their speed and drift velocity decreases, so current decreases so it’s resistance increases
Where are semiconductors used?
Sensors
Why do semiconductors have a higher resistivity than metals?
Because there are fewer charge carriers available
What happens to a semiconductor if energy is supplied to the semiconductor? (Only occurs with some semiconductors)
More charge carriers are released so the current is increased and their resistance and resistivity decreases
What are three semiconductor components?
- Thermistors
- LDRs
- Diodes
What does the resistance of a thermistor depend on?
Temperature
What is an NTC thermistor?
Negative Temperature Coefficient - which means the resistance decreases as temperature goes up
The resistance of an NTC thermistor [……..] with temperature
Decreases
How does warming a thermistor decrease resistance?
Warming the thermistor gives the electrons enough energy to escape from their atoms, means the more charge carriers are available, so current increases and resistance decreases.
What does the resistance of an LDR depend on?
Light Intensity
What does LDR stand for?
Light Dependant Resistor
The greater the intensity of light shining on an LDR, the [……] it’s resistance
Lower
How does a greater light intensity lower an LDRs resistance?
Light provides energy that releases electrons, this means there are more charge carriers which means there is a higher current and a lower resistance
Diodes only let current flow in […….] direction
One
What are Diodes designed to do?
To let current flow in one direction
What is forward bias?
Is the direction on which the current is allowed to flow in a diode. It’s the direction of the arrow in the circuit symbol
What is a Diodes threshold voltage?
0.6V
What is a Threshold Voltage for a Diode?
The threshold voltage is the minimum voltage needed to create a conducting path along the diode.
In the reverse bias (reverse direction) the resistance of the diode is very…
High
In the reverse bias (reverse direction) of a diode the current that flows is very…
Tiny
