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

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

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

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

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

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?

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?

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

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  

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

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.

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.

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?