Download Ohmic and Non-Ohmic Devices

Year 11 Physics
Ohmic and Non-Ohmic Devices
Aim: To investigate the voltage-current characteristics of some common circuit components
A formal report is not required for this practical exercise. You are to use Crocodile Clips to construct 3
circuits, answer questions, tabulate measurements and use Excel to produce graphs. Staple the completed
instruction sheets to a printout of all three circuits and the three line graphs. Make sure all sections are fully
labelled, and your name is on all sheets. Write a conclusion that relates the aim to each component tested.
Circuit 1:
1 Create a circuit with a battery, 2 resistors and ammeter in series.
Add a voltmeter across one of the resistors.
2
Change the battery voltage (emf) from 9V to 10V by clicking on the
number above the symbol and completing the resulting table as
shown below left.
3
Change the resistance from 10k (10000) to 100 by clicking on the
number above the symbol and completing the resulting table as
shown below right.
4
Label this circuit: Circuit 1 (Resistor) by opening
the Add menu and choosing Text. Type your label
then drag it into place. Double click to alter the text.
5
Record the current through and the voltage across
one of the resistors for a variety of batteries,
eg. 10V, 8V, 6V, 4V, 2V.
Voltage across
Resistor
V
Current through
Resistor
I
V
I
Note: the voltmeter and ammeter automatically
change units at times so make sure you record the
unit as well as the size of V and I.
6
What current would you expect to flow through
the resistor when V = 0 volts?…………………
Add this to your table.
Maureen Trotter - Monbulk College – Year 11 Physics – Ohmic and Non-Ohmic Devices Prac
7
Two facts about V/I should be apparent from your table. What are they?
……………………………………………………………………………………………………..………...
……………………………………………………………………………………………………..………...
8
Use Excel to graph V against I (V on the vertical scale, I on the horizontal). Make sure you correctly
label both axes and include a heading (eg. V-I Characteristics of a Resistor). Remember also to convert
all measurements to consistent units (eg. all V or mV, not a mixture of both).
9
Is the resistor an ohmic device? ……………………………………………………………………………
Explain: ………………………………………….…………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
Circuit 2:
1. Create a circuit with a 10V battery, filament lamp, 100 
resistor and ammeter in series. Add a voltmeter across the lamp.
2. Change the battery voltage and resistance as you did in circuit 1.
3. Label this circuit: Circuit 2 (Filament Lamp).
4. Record the current through and the voltage across the filament
lamp for a variety of batteries, eg. 10V, 8V, 6V, 4V, 2V.
Remember to record the unit as well as the size of V and I.
5. What current would you expect to flow through the
filament lamp when V = 0 volts? ………………….
Add this to your table.
6. Use Excel to graph V against I. Make sure you
correctly label both axes and include a heading
(eg. V-I Characteristics of a Filament Lamp).
Voltage across
Filament Lamp
V
Current through
Filament Lamp
I
V
I
Remember also to convert all measurements to
consistent units (eg. all V or all mV).
7. What do you notice about V/I for the filament lamp?
………………………………………………………
………………………………………………………
8. Is the filament lamp an ohmic device? …………………
Explain: ………………………………………….……………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
Maureen Trotter - Monbulk College – Year 11 Physics – Ohmic and Non-Ohmic Devices Prac
Circuit 3:
1 Create a circuit with a 10V battery, diode, 100  resistor and
ammeter in series. Add a voltmeter across the diode. Make
sure that the battery and diode are facing the same way as in
the circuit diagram. This ensures that the diode is forward
biased.
2 Change the battery voltage and resistance as you did in circuit 1.
3 Label this circuit: Circuit 3 (Forward Biased Diode)
4
Record the current through and the voltage across the diode
for a variety of batteries, eg. 10V, 8V, 6V, 4V, 2V, 1V, 0.7V,
0.5V, 0.3V, 0.1V. Remember to record the unit as well as the size
of V and I.
5
What current would you expect to flow through the diode when V = 0 volts? ……………..…………….
Add this to your table.
6 Use Excel to graph V against I. Make sure you
correctly label both axes and include a
heading (eg. V-I Characteristics of a Diode). Remember also to convert all measurements to
consistent units (eg. all V or all mV).
Voltage across Current through
V
7 What do you notice about V/I for the diode?
Diode
Diode
I
………………………………………………………
V
I
………………………………………………………
8
Is the diode an ohmic device? …………………….…
Explain:………………………………………….……
………………………………………………………
…………………………………..………………………
…………………………………….………………
………………………………………………………
9
Reverse bias the diode (replace with a diode facing the
other way, or reverse the battery)
10 Label this circuit: Circuit 3 (Reverse Biased Diode)
11 Record I and V for battery voltages of: 1V, 10V, 100V,
200V, 300V, 400V. Add these results to your graph.
12 Why is it difficult to produce a V-I graph for a diode to
scale?
…………………………………………………………
…………………………………………………………
13 Name a use for a diode which uses the fact that for low
voltage supplies there is no current through a reversebiased diode
……………………………………………………….…
Maureen Trotter - Monbulk College – Year 11 Physics – Ohmic and Non-Ohmic Devices Prac