12.1.1 Like Charges Repel, Unlike Charges Attract

As you probably already know: like charges repel, unlike charges attract. But what are charges?

The mother of all charges are the electron and the proton, which carry a charge of −e and +e respectively (e denotes the elementary charge of $\displaystyle 1.60\times {{10}^{{-19}}}$ coulomb).

\displaystyle -e=-1.60\times {{10}^{{-19}}}\text{ C}

A neutral atom is neutral in charge because it contains the same number of electrons as protons. When neutral atoms gain or lose electrons, they become negative and positive ions respectively. When the atoms in an object become ionised (through friction perhaps), the object become charged. Some people have the misconception that a positively charged object contains only protons and no electrons. That’s not true of course. A positively charged object merely contains more protons than electrons.

Do realize also that 1 C is a huge amount of charge. One has to lose or gain 6 250 000 000 000 000 000 electrons or protons to accumulate that amount of charge. A typical lightning discharges 15 C.

Come to think of it, “like charges repel, unlike charges attract” is such an ingenious design. I mean, if like charges were to attract and unlike charges repel instead, the resulting chemistry would be nowhere as rich and fascinating.

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Video Explanation

Like Charges Repel, Unlike Charges Attract (with demo)

How to Calculate Resultant Electric Force

Demonstration

Fun Fly Stick

Van der Graaff and Tinsel Foil

Applets

Balloon and Static Electricity (PhET)

John Travolta (PhET)

Interesting

It’s All Electric!