IV graphs Flashcards
What components do I need to measure the resistance of a resistor?
- Ammeter
- Voltmeter
- Variable resistor
Why is a variable resistor needed?
- Changes current of circuit
- Changes P.D across component
- GET A RANGE OF VALUES
OR…. other way
What are the 2 ways in this experiment that I can increase the voltage?
- By powerpack
- By variable resistor
How do you collect negative results for P.D and current?
- Switch terminals of battery around.
What does the straight line graph of a resistor tell you about its resistance?
- Shows resistance is constant.
What is the relationship between P.D and Current in graph of resistor?
- Directly proportional relationship
What is an “ohmic conductor?”
- One that obeys Ohms Law
- P.D and current are directly proportional and temp is constant.
Q.)
Describe how to use variable resistor to vary the current in the circuit.
- Adjust the variable resistor to increase resistance through it.
- Increasing resistance through it decreases current of overall circuit.
What happens to the brightness of the filament bulb when we increase P.D?
- Brightness increases
- More energy transferred
What happens to the resistance of a filament lamp as brightness increases?
- Resistance increases as brightness does.
What happens to the resistance of the lamp as you increase the P.D across it ?
- The resistance increases as you increase P.D.
Why does an increase in temperature increase resistance?
- Metal ions vibrate more
- Flow of electrons is more difficult.
- The resistance increases.
What causes the increase in temperature in a filament bulb?
The increase in current.
How is the steepness of a line related to resistance on an IV graph?
- Steeper line: lower resistance
- Shallow line: high resistance
Why does a shallow line have a high resistance?
- Low current for the same PD
If the axis on IV graph changes to V on y and I on x… what happens to resistance?
Shallow line = low resistance
Steeper line = high resistance
low P.D. = low resistance
High P.D = high resistance
What is the variable resistor changing when you experiment I + V in diodes?
- Current through diode
- see effect on P.D
What are the steps to completing the IV experiment for diode?
1.) Set up electrical circuit as shown
2.) Adjust variable resistor (take new values for current + PD.)
3.) Repeat to collect 5 readings
4.) Switch terminals aroud to plot negative values
5.) Negative direction = Zero!!
What type of resistance does diode have in poisitive direction?
- Low resistance
What is a thresh hold voltage?
- This is the voltage needed for current to flow through.
Why is a thresh hold voltage useful?
- Prevents current “accidently” flowing in opposite direction.
Q.)
Use the Diode IV graph to explain why current passes through diode.
(3 points)
- It has reached thresh hold voltage
- Current flowing in correct direction
- Low resistance when voltage is positive.
Give a descritpion of a filament lamp.
- Has a thin wire that heats up and emitts light.
- Non- ohmic conductor
Q.)
How can you tell that an IV graph is a diodes’ in terms of resistance?
- High resistance in one direction
- Low resistance in other direction
Which type of graph obeys Ohms Law and has a constant resistance, linear or non- linear?
- Linear graphs
What are non- linear graphs?
- Ones that donnot obey Ohms Law and have varying resistances due to changes in temperature.
Give examples of non- linear elements.
- Filament bulb
- Diode
- Thermistor
- LDR
Give examples of linear elements.
- Wire
- Resistor
What is meant by the term “negative potential difference?”
- Potential difference values are in opposite direction ie. negative…
Why do we add an extra resistor when we investigate IV graphs for diodes?
- Lowers the current
- BECAUSE the current is low we need a miliammeter.
