Simulation of I-V graph of Non-Ohmic conductor
It is a 3D interactive lab bench for AQA GCSE Physics Required Practical 4, investigating how current through a component varies with potential difference across it. Pupils build a series test circuit on screen, sweep the potential difference, take readings, and watch the characteristic graph build up point by point.
The apparatus. A low voltage supply, ammeter and voltmeter sit on a raised shelf at the back. On the board in front are a variable resistor (rheostat) with a sliding contact, a swappable test component, and a switch. The voltmeter connects in parallel across the component; everything else is in series. When the diode is selected, a protective resistor labelled P appears in the circuit and the ammeter switches to reading in milliamps, matching how the real practical is done.
The three components. Pupils switch between a fixed resistor, a filament lamp, and a diode using the buttons at the top. Each produces its correct characteristic. The resistor gives a straight line through the origin because it is ohmic and its resistance stays constant. The filament lamp gives a curve that bends over and flattens, because the filament heats up and its resistance rises. The diode shows almost no current until about 0.7 volts, then a steep rise, plotted in milliamps over a small voltage range, because the potential difference across a diode barely climbs past its knee.
The procedure. Seven guided steps run along the bottom: build the circuit, set the potential difference, close the switch, read voltage and current together, log the point, repeat for every setting, and plot current against potential difference. A clear instruction panel and a spoken announcement accompany each step. The graph plots current on the y axis against potential difference on the x axis, reveals each point in turn, then draws the best fit curve and a short conclusion.
Accessibility (the Adapt menu). Dark theme, Irlen colour overlays, colour blindness filters, a reading ruler, dyslexia spacing, adjustable text size, high contrast, projector mode, reduce motion, slow animation, and a buttons only mode for pupils who cannot drag. The whole thing runs from the keyboard and works on screens from a phone up to an interactive whiteboard.
Suggested class activity: “Name that component”
A one lesson enquiry that turns the graph shape into a diagnostic skill.
Starter (5 minutes). Show the resistor sweep on the board without naming it. Ask pupils to predict, in one sentence, what a graph of current against potential difference will look like and why. Take a few answers, then run the reading and reveal the straight line.
Main task (25 minutes). Pupils work in pairs, each pair given one component in a fixed order but told only “component A, B and C”. Their job is to produce all three graphs and, from the shapes alone, decide which is the resistor, which is the lamp, and which is the diode, justifying each choice with the physics. Ask them to record for each component a results table, a sketch of the graph, and one sentence explaining the shape. The buttons only mode keeps the focus on reasoning rather than mouse control, and the milliamp scale on the diode is a deliberate clue worth discussing.
Stretch questions. Why does the lamp graph flatten rather than stay straight? What is happening to the electrons and the metal ions inside the filament as it heats? Why is a protective resistor needed with the diode, and why does the voltmeter still read only the diode? What does the gradient of the resistor line tell you, and how could you use it to find the resistance?
Plenary (10 minutes). Pairs swap their three sketches with another pair, who must name the components cold. Finish with a quick vote on the trickiest one to identify and a class explanation of the giveaway feature for each shape, ohmic straight line, heating curve, and one way conduction.
Assessment for learning. Circulate while pairs are deciding and listen for the reasoning, not just the right label. The common misconception to catch is pupils calling the lamp non ohmic without linking it to temperature and resistance, so probe that link directly.