Resistance and the ohm
The constant has a name. It is the property that decides how much current a given push produces, and every conductor has its own value of it.
Electrical resistance
V / I = R
The constant V ÷ I is called the electrical resistance of the conductor, written R.
The unit
The unit in which resistance is measured is the ohm, written with the Greek letter omega.
One ohm
If a potential difference of one volt applied across the two ends of a conductor makes a current of one ampere flow through it, the resistance of that conductor is defined as one ohm.
1 Ω
The instrument used to measure resistance is called an ohm meter.
The graph the readings make
Take the data from the activity, mark the potential difference up the y axis and the current along the x axis, and plot it. The points fall on a straight line through the origin — which is what "directly proportional" looks like when you draw it.
| I (A) | 0.5 | 1 | 1.5 | 2 | 2.5 |
|---|---|---|---|---|---|
| V (V) | 1 | 2 | 3 | 4 | 5 |
The gradient of that line is the resistance
Because every point satisfies V ÷ I = R, the steepness of the line is R. A steeper line means a larger resistance: more volts needed for each ampere you want.