Potential Difference and the Earthed Point
A 3D circuit with a real earth rod driven into the ground, and a landscape of potential floating above it: one column per node, rising above the zero rail or hanging below it. Move the earth clip and the entire landscape slides, yet not one difference changes — take the clip off and the potentials become unknowable while V_AB is still 12 V.
Cara memakai simulasi ini
- Press Earth at A, Earth at O or Earth at B to move the zero of potential around the circuit
- Press No earth to remove the reference altogether and watch the columns lose their footing
- Use Side-on view to read the heights of the columns against the zero rail
- Press Reset to return the earth clip to its original node
Yang perlu diamati
- Moving the earth clip slides every column up or down by the same amount
- Every potential difference in the circuit is unchanged by where the earth is placed
- Nodes can sit below the zero rail, giving perfectly ordinary negative potentials
- With no earth the individual potentials are undetermined but the differences are not
- A voltmeter always reads a difference, which is why it never needs the earth to work
Fisika di baliknya
Only differences in potential are physically meaningful, because only a difference does work on a charge: W = qV_AB. Assigning zero to a chosen node is a free choice, and earthing is simply the standard way of making that choice explicit. Shifting the reference adds the same constant to every node's potential, so every difference V_AB = V_A − V_B survives untouched. Without any reference the individual potentials have no determined value at all, while the differences between them remain exactly as measurable as before.