Simulation of I-V graph of Ohmic conductor
I–V GRAPH OF AN OHMIC CONDUCTOR
An ohmic conductor obeys Ohm’s Law — double the voltage, double the current. This simulation lets students build the I–V graph themselves by setting the voltage and plotting real data points. Every point lands exactly on a straight line passing through the origin, which is the defining characteristic of an ohmic conductor. Changing the resistance changes the gradient of the line: a lower resistance produces a steeper line because more current flows for the same voltage.
The gradient of the line equals 1/R — so the graph is not just evidence of Ohm’s Law, it is a method for measuring resistance.
Class Activity: Building the Graph from Scratch
Objective: Students collect their own data, plot the I–V graph, and calculate resistance from the gradient.
- Set R to 20 Ω. Start with V = 0 and increase in steps of 2V, releasing the slider at each step to plot the point. Record V and I in a results table.
- Draw the line. Once six or more points are plotted, observe that they form a straight line through the origin. Ask: what does it mean if the line does NOT pass through the origin?
- Calculate resistance from the gradient. Pick two points on the line and apply: R = ΔV ÷ ΔI = 1 ÷ gradient Compare the answer to the resistance shown on screen. They should match exactly.
- Change R to 40 Ω. Repeat the experiment. Plot the new line on the same graph (use the reset button to start fresh). Ask: which line is steeper? Why? Establish that a steeper gradient means lower resistance.
- Exam question: “Explain why a straight line through the origin on an I–V graph shows that a component is ohmic.” Students write a three-sentence answer using evidence from the simulation.