In this long-life battery, an alkaline electrolyte (potassium hydroxide) is mixed with powdered zinc. A porous sleeve separates the ‘ mixture from a manganese-dioxide lining.

A metal ‘nail’ collects electrons (current) from the zinc and takes them to the negative terminal. The electrons flow on through the torch bulb to the steel case at the positive terminal, and then into the manganese dioxide to replenish electrons it loses to the electrolyte.

Neutral atom The nucleus of an atom is positively charged. Its electrons are negative. So the whole atom is neutral.

Positive ion Loss of an electron results in the atom becoming positively charged. It is then called a positive ion.

Negative ion When an atom gains one or more electrons, it becomes negative and is called a negative ion.