Energy and Voltage in Circuits
4 marks · NormalThe table below shows the results of an experiment to investigate the current through a wire as the voltage is increased.
| Voltage (V) | Current (A) |
|---|---|
| 0.5 | 0.10 |
| 1.0 | 0.20 |
| 1.5 | 0.30 |
| 2.0 | 0.40 |
| 2.5 | 0.50 |
a) Plot a graph of current (y-axis) against voltage (x-axis), and draw the best fit straight line.
b) Use your graph to state the relationship between current and voltage for a wire at constant temperature.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Line straight through the origin; points accurately plotted. · must show Accurate plotting of points, Best fit straight line through origin, Axes correctly labelled with units
(b) Current is directly proportional to voltage (at constant temperature).
Must show: Straight line through the origin; appropriate scale; points plotted; relationship stated.
Common mistakes: Plotting wrong axes; Not starting from origin; Relationship described incorrectly
Show mark scheme and worked solution
Marking points
P1 (a) · 1 mark · Plots all points accurately.
P2 (a) · 1 mark · Draws best fit straight line through the origin.
P3 (a) · 1 mark · Labels axes with units, uses suitable scale.
B1 (b) · 1 mark · States that current is directly proportional to voltage at constant temperature.
Worked solution
b) The graph is a straight line through the origin: current is directly proportional to voltage (Ohm’s law).