Page 53 - Innovator's Science-8

connected to the negative terminal of the battery]. A glowing LED indicates
that your cell is working. In this cell, the metal electrodes are the copper

wires and the iron nails. The electrolyte is the lemon juice, which helps
conduct electricity. You may also use salt solutions instead of lemon juice.
Some common metal pairs for Voltaic cells are zinc/copper, zinc/ silver,

aluminium/copper, iron/copper, magnesium/copper, and lead/copper.
Some metals such as copper act as positive electrodes, while others like
zinc act as negative electrodes. This is due to their chemical properties. We

will learn more about this in the higher grades.
Dry Cells

Voltaic cells were a great scientific discovery, but they are not practical for
everyday use because they contain liquid electrolytes. In modern times,

dry cells are commonly used instead. They are called “dry” because their
Metal cap electrolyte is a thick moist paste instead of a liquid. A dry cell
has a zinc container that serves as the negative terminal, and
Carbon rod
in the center, there is a carbon rod with a metal cap that serves

Electrolyte as the positive terminal. The paste-like electrolyte fills the
space between them. However, dry cells can only be used
Zinc container
once; when the chemicals are used up, the cell stops
producing electricity and must be thrown away. For many

(a) (b) devices today, rechargeable batteries are preferred because
(a) Dry cell; they can be used repeatedly.
(b) Its internal structure
Rechargeable Batteries

Rechargeable batteries are special types of batteries that can be used over
and over again by recharging them when they run out of power. This helps
reduce waste and saves money in the long run. They come in many sizes
and types, depending on their use—from small ones in watches and mobile
phones to larger ones in laptops, tablets, inverters, and even electric

a. vehicles. However, rechargeable batteries do not last forever. After many
charge and discharge cycles, they begin to lose their ability to hold power
and eventually need to be replaced.

b.

d. e. f.
Typical rechargeable batteries used in a. Laptops; b. Mobile phones;
c. c. Camera; d. Inverter; e. Vehicles; f. Charging a mobile phone

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Science-8