Charge and Force

Like Charges Repel

matching signs push apart

Two charges with matching signs push away from each other. The force arrows are equal in size and opposite in direction.

Example

Two charges with matching signs push away from each other. The force arrows are equal in size and opposite in direction. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Both charges are positive

Put a positive 2 coulomb charge on the left and a positive 3 coulomb charge on the right.

qleft=+2 Cqright=+3 Cq_{\text{left}} = +2\ \text{C}\qquad q_{\text{right}} = +3\ \text{C}
Like chargesTwo positive charges push away from each other.+2 Cleft+3 Cright6 N6 N

Matching signs repel

Because the signs match, the left charge is pushed left and the right charge is pushed right. The arrows point away from the space between the charges.

+ with +⇒repel+ \text{ with } + \Rightarrow \text{repel}
Like chargesTwo positive charges push away from each other.+2 Cleft+3 Cright6 N6 N

The force pair has equal size

The left force and the right force have the same size, 6 newtons, but opposite directions. The helper checks that pair before the diagram can render.

Fleft=Fright=6 NF_{\text{left}} = F_{\text{right}} = 6\ \text{N}
Like chargesTwo positive charges push away from each other.+2 Cleft+3 Cright6 N6 N

Equal size survives every allowed size

The diagram draws the 6 newton row. Other exact rows keep the same contract: left and right force sizes match, while the arrows point away from the middle.

FleftFright4 N4 N6 N6 N8 N8 N\begin{array}{c|c}F_{\text{left}}&F_{\text{right}}\\4\ \text{N}&4\ \text{N}\\6\ \text{N}&6\ \text{N}\\8\ \text{N}&8\ \text{N}\\\end{array}
Like chargesThe middle table row is the checked diagram.+2 Cleft+3 Cright6 N6 N
electrostatics Matching charge signs make the force pair point away from the space between the charges.