Tag: physics

A depolarizer in electrochemistry is a synonym of electroactive substance, i.e., a substance which changes its oxidation state, or partakes in a formation or breaking of chemical bonds, in a charge-transfer step of an electrochemical reaction. In the cells, the term "depolarizer" has been used to denote a substance used in a primary cell to prevent buildup of hydrogen gas bubbles.

By convention, current is assumed to travel from positive to negative direction. The electrons travel from negative to positive. The direction of current is not the same as direction of flow of electrons; they are opposite.

The ideal qualities of standard cells as follows:
(1) The cells must be constructed from high purity materials and be reproducible.
(2) Except when current is flowing there should be no chemical reaction taking place in the cell.
(3) When the cell is thermally cycled it must give the same emf at a given temperature regardless of its thermal history.
(4) When a current is passed through the cell, its emf may change, but it must recover rapdidly and completely on cessation of the current.

(1) to (4) above represent an ideal qualities which only the Weston Standard cell approaches. The Weston Standard cell is constructed with the basic materials- mercury, cadmium, sulfuric acid, and water- are all purified by distillation, starting with the purest materials available. Hence out of given cells cadmium cell is the standard cell.

Alarm clock uses Dry Cell. Rest of the components work on power supply.

When the ends of the metal wire are not connected to a battery, no electric field is produced inside the wire. Thus no force acts on the electrons in the wire. So the electrons collide with each other and move in random directions.

Nickel cadmium cells are used in portable machines that run on electricity. It is rechargeable.

Lithium cell has a negative plate of lithium iron phosphate and a positive plate of carbon. It is also called as button cell.

Electrons are termed as negative charged particles. Thus when electrons move from negative electrode to positive electrode, we say that negative particles move from negative electrode to positive electrode. On the other hand, the positive charges get attracted towards the negative electrode, thus they move from positive electrode to negative electrode.

Dry cell are not rechargeable.