Connecting a cell

The free electrons are already moving. A cell does not set them going — it gives their movement a direction.

Figure to be added

Figure 19.7 — a metal conductor with its two ends joined to the terminals of a dry cell, an arrow along the conductor marking the direction in which the electrons flow.

What each terminal does

The negative terminal

Holds a force that pushes electrons away — it repels them.

The positive terminal

Holds a force that pulls electrons towards it — it attracts them.

So the drift begins

Join the two terminals of a cell with a conductor and electrons immediately begin to flow through the conductor, from the negative terminal towards the positive one. They can only do this because of the free electrons already present in the conductor — the random wandering of the last page becomes a movement in one direction.

Random motion in every direction → One direction, negative to positive

The cell steers; it does not supply the electrons

The electrons were in the wire before the cell was connected. What the cell adds is a reason for them all to drift the same way — which is why a bulb lights the instant the circuit is completed rather than waiting for electrons to arrive from the battery.

Electrons flow from negative to positive

Inside the conductor, the electrons travel from the negative terminal of the cell to the positive one. Hold on to that, because the next page defines something that runs the other way.