✔ 最佳答案
咁點解在這點之後去到battery既wire 仲有current
Current would flow when there is a potential difference. Earthing a point in the circuit only defines that point is at earth potential (i.e. zero volt). There will not be any current leaking to earth from that point because both (the point and earth) are at the same zero potential. There is no potential difference to drive current to flow to earth.
The battery maintains a potential difference in the circuit. As long as the circuit is complete, the potential difference given by the battery casues current to flow.
同埋果段wire既potential係negative(如果有resistors), 好似好怪, negative 又有冇意思?
Potentials can be +ve or -ve, or even zero. As said above, current flows because of potential difference. A point "after" the earthing point (in the direction of current flow) is obviously below earth potential (zero volt), hence would have negative potential value. It is because of the difference of potential between the earthing point (zero volt) and the point in question (a -ve potential) that drives the flow of current.
咁earth左又有咩用?
Generally, earthing provides steady potentials at all points in the circuit.