Electrical cells
Electrical cells are the sources of electric current.
(a)     Types of electrical cell :    (i) primary     (ii) secondary
(i) Primary Cells : The cells which cannot be charged again and again are known as primary cells.
Example : Voltaic, Daniel, laclanche and dry cells.
(ii) Secondary Cell : The cells which can be charged again and again are known as secondary cells.
Example :  Edison cell, lead-acid accumulator

*    Note : combination of cell is known as battery.

Circuit diagrams and circuit symbols
Scientists use certain symbols to draw electrical circuits. An electrical circuit drawn using these symbols is called a circuit diagram. The symbols used to indicate different components are called circuit symbols. Figure shows some components and their circuit symbols.

An electrical circuit in symbols :

Requirements of a Circuit
Suppose that you were given a small light bulb, an electrochemical cell and a bare copper wire and were asked to find the four different arrangements of the three items that would result in the formation of an electric circuit that would light the bulb.
4 different attempts

In attempt A, the wire does not loop back to the negative terminal of the cell. In attempt B, the wire does form a loop but not back to the negative terminal of the cell. In attempt C, there is no complete loop at all. Attempt D resembles attempt B in that there is a loop but not from the positive terminal to the negative terminal. And in attempt E, there is a loop and it does go from positive terminal to negative terminal; this is a circuit but the light bulb is not included as part of it.