Tag: electricity

Many devices such as----------------use battery 

Answer is C.

When a primary cell is used, chemical reactions in the battery use up the chemicals that generate the power; when they are gone, the battery stops producing electricity and is useless. In contrast, in a secondary cell, the reaction can be reversed by running a current into the cell with a battery charger to recharge it, regenerating the chemical reactants. 
The types of cells mentioned in option A and option are correct.
Hence, option C is correct.

When dissolved in fluid, salts tend to break apart into their component ions, creating an electrically-conductive solution. Common salt is one such salt. common salt is  $ NaCl$ which gives $Na^+$ and $Cl^-$.

Ammonium chloride, as a paste, is the electrolyte in a dry cell. Hence the above statement is false.

the Daniel cell is a type of electrochemical cell invented in 1836. it is consisted of a copper pot filled with a copper sulfate solution , in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode. Daniel cell is also called Zn-Cu cell and has constant e.m.f of 1.08 volts.

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.