1. Equipment
REQUIRED PRACTICAL.. This is a series of 3 practicals with graphs that need to be drawn. This will take multiple lessons
Guidance for each practical is in the notes. Students WILL struggle to wire the diode circuit in particular so spend a bit of extra time on setup as the 3 practicals are VERY similar but use different power pack voltages.
They will need to do each practical twice, one for positive polarity, once for negative (Results should be identical for Resistor and Bulb but with a minus) resulsts should be 0 current in the negative direction for diode)
Electric Circuit kits
12v Fillament bulbs
Ammeters
Voltmeters
Multimeters
LEDs
10 ohm Resistors
100 ohm resistors
Crocodile clips
See if students can remember the measurement of energy

2. Component test – What are they?
Recap Quiz
Component test – What are they?
Battery
Ammeter
Lamp
Quick test, Students are not allowed to look back in their books!
Switch
Thermistor
Variable Resistor

3. Lesson intentions:
To carry out an investigation of how the resistance of components can change.
Date and title: Component characteristics
9 April, 2019
S t e p s
t o
S u c c e s s
Learning outcomes: 4
Identify components from simple I–V graphs
Describe the resistance characteristics of a filament lamp.
Explain the resistance characteristics of a filament lamp in terms of electrons and ion collisions. 6 12 8
Key words: Diode, Resistor, LDR, LED, Thermistor

4. Bigger picture Topic Potential difference and resistance
Component characteristics
Current and charge
Series Circuits
Topic
Electric Circuits
Parallel Circuits

5. New Components! Light dependent resistor
Resistance changes with the amount of light
Thermistor
Resistance changes with the temperature
New symbols and a recap of thermistor.
Students just need to know what the thermistor and LDR do. They need to experiment with the diode.
Ask students what the function of the first 2 components are before revealing
Diode and Light emitting diode
Allows current to flow in one direction only

6. Light Dependent Resistor (L.D.R)
Resistance changes with the amount of light
Students need to make a sketch graph.
And answer the question.
Camera shutter control, security lights, Street lights, Proximity sensors in phones (phones turn the screen off when you hold it to your ear)
What might an LDR be used for?

7. Thermistor Thermistor Resistance changes with the temperature
Students need to make a sketch graph.
And answer the question.
Digital thermometer, kettles, fire alarms, fan control in a computer
What might a Thermistor be used for?

8. Current and P.D in a Resistor
A resistor has a fixed resistance.. What happens to the current if we increase the Potential difference?
Power Pack Voltage
(V)
Potential Difference (V)
Current
(A) 1 2 3 4 5
100 Ω A V
This is a required practical.
Talk the students through the practical, particularly how to set it up. This will involve reversing power cables and can be confusing so spend a little extra time setting up.
They will essentially do the same practical 3 times to get 3 sets of results to plot 3 graphs with
A 100 ohm resistor is used in this circuit Crocodile clips will hold the resistor in place.
They will need to do each experiment TWICE.
The FIRST time the ammeter and voltmeter must read positive
The SECOND time the follow EXACTLY the same procedure, but they Switch the cables that come out of the power pack around, (so the volt and ammeter now read minus)
This just changes the direction of current around the circuit

9. Current and P.D in a Filament bulb
A filament bulb produces light.. What happens to the current if we increase the Potential difference?
Power Pack Voltage
(V)
Potential Difference (V)
Current
(A) 2 4 6 8 10 12 A V
This is a required practical.
THE CIRCUIT IS EXACTLY THE SAME.. THEY JUST NEED TO SWITCH THE RESISTOR FOR A BULB
A LARGE 12v bulb is used in this experiment
They will need to do each experiment TWICE.
The FIRST time the ammeter and voltmeter must read positive
The SECOND time the follow EXACTLY the same procedure, but they Switch the cables that come out of the power pack around, (so the volt and ammeter now read minus)
This just changes the direction of current around the circuit

10. Current and P.D in a Diode
An LED produces light.. What happens to the current if we increase the Potential difference?
Power Pack Voltage
(V)
Potential Difference (V)
Current
(mA) 2 3 4 5 6 mA V
This is a required practical.
THE CIRCUIT IS SLIGHTLY DIFFERENT
A 10 ohm resistor must be wired in parallel and a Multimeter must be wired in instead of the ammeter
Putting wires in the ammeter (Important so as not to damage the multimeter)
Place the black lead into the COM port
Place the red lead into the V port
Turn the dial to the RIGHT until you get to 200m
A Blue LED is Used.
YOU MUST HIGHLIGHT TO THE KIDS THAT THE LONG LEG IS POSITIVE… POLARITY IS IMPORTANT IN THIS EXPERIMENT
The bulb will not light at 1v but should at 2v (If it does not light, the LED could be the wrong way around or the LED may be broken)
POWERPACKS MUST NOT BE LEFT ON FOR LONG PERIODS OF TIME, VOLTAGHE MUST NOT EXCEDE 6V!
They will need to do each experiment TWICE.
The FIRST time the ammeter and voltmeter must read positive
The SECOND time the follow EXACTLY the same procedure, but they Switch the cables that come out of the power pack around, (so the volt and ammeter now read minus)
This just changes the direction of current around the circuit

11. Plot data on a graph!
Plot Potential Difference on the X, Current on the Y
These graphs must be quadrant graphs.. Students will STRUGGLE to plot these. I recommend borrowing a digitiser from Maths and doing the resistor example on the board. As a class.
They should have 3 separate graphs , one for each component.
The lines of best fit will be tricky for the bulb and diode. Bulb is s shaped.. The diode will be flat and then sharply rise.
For extra practice, you can have the student calculate the resistance from the data provides, although not essential.

12. What did you see and why?
What happens to the current as you increase or decrease the voltage? Describe what you see for each graph
Describing graphs is difficult, they may need guiding through.

13. Which component follows Ohm’s Law?
Resistor
Filament lamp
Diode
Their graphs should look like these.
The resistor follows Ohms law.
Ask why the Filament bulb and diode don’t follow ohms law… use a variety of verbal or pupil models to do this.
Filament bulb: more voltage = larger energy transfer as hear. More heat, more particle movement, more particle movement = increased resistance, current odoes not increase proportionally at higher voltages
Diode: only allows current in one direction so cannot follow ohms law.
Students write their own versions of the explanations for the plenary.
Ohm’s law states that electrical current is proportional to the potential difference.
Which component follows Ohm’s Law?