SS3 First Term Physics Lesson Note – Electric Cells

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WEEK 4

ELECTRIC CELLS

• Electric Circuit
• Types of Electric Cells

ELECTRIC CIRCUIT

Electric current is simply electric charge in motion. Electric cells are chemical devices, which are capable of causing an electric current to flow. This produces electric force, which pushes the current along.

Electrons flow from the negative terminal or cathode of the cell to the positive terminal or anode

TYPES OF ELECTRIC CELLS

Electric cells are divided into two namely: the primary cells and the secondary cells

PRIMARY CELLS – These are those cells in which current is produced as a result of an irreversible chemical charge.

SECONDARY CELLS – These cells are those which can be recharged when they run down by passing current backwards through them.

There are three components in a cell. Viz:

1. The anode (positive electrode)
2. The cathode (negative electrode)

• The electrolyte

THE SIMPLE PRIMARY CELL (VOLTAIC CELL)

A simple cell can be made by placing two different electrodes (metals) in an electrolyte. Two wires are then used to connect these metals to a voltmeter. If a deflection is noticed it means that the cell creates a voltage.

Defects of a simple cell

The two major deflects of a simple all are polarization and local action

1. Polarization – This cell defect is characterized by the release of “hydrogen bubbles.” The bubbles collect at the positive electrode and insulate it. This show down and eventually stops the working of the cell.

This defect can be corrected either by occasionally brushing the plates, which is highly inconvenient, or by using a depolarizer e.g. manganese oxide.

1. Local action – This occurs when impure zinc is used. The impurities in the zinc result in the gradual wearing away of the zinc plates. This can be prevented by cleaning the zinc with H₂SO₄ and then rubbed with mercury. The mercury amalgamates the zinc by covering the

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