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.

Electric Conductors and Insulators

Conductors - Materials that allow electricity to flow through them easily.

Insulators Materials that do not allow electricity to pass through them.

• Human body is a conductor, so touch a current carrying wire is detrimental and so insulating it prevents from an electric shock.
• Some examples of conductors are: Metals like copper, Iron
• Some examples of insulators are: Rubber, Plastic

This sign is used in areas which are near electric junctions as a warning.

Electrical Safety

Electricity can be very dangerous if you do not handle electrical devices carefully. One should never play with electrical wires and sockets. Electricity from cells is safe and you can experiment with it, but you have to be careful not to connect the two terminals of a cell directly through a wire/conductor. Electricity generated by portable generators is dangerous and should not be used for experiments.

A demo video link to understand the working of Electric Circuit

https://youtu.be/GMS6SUYqsMM

Conclusion:

• Source of electric current: A device that can be used to produce an electric current is called a source of electric current.
• Electric circuit: A path for an electric current to flow is called an electric circuit.
• Closed-circuit: A circuit that has an ‘unbroken path’ through which an electric current can flow is called a closed circuit.
• Open circuit: A circuit with a break in it is called an open circuit.
• Electric switch: A device that is used to open or close a circuit is called an electric switch.
• Conductor (in this chapter): A material that allows electric current to pass through it easily is called conductor.
• Insulator (in this chapter): A material that does not allow an electric current to pass through it easily is called an insulator.
• In a dry cell, a chemical reaction takes place to produce an electric current.
• A dry cell contains solid or semisolid ingredients.
• All cells have two terminals: the positive and the negative terminal.
• Electric current flows only if there is an unbroken or complete path, starting from one terminal of the source, through various devices back to the other terminal of the source.
• An electric switch is a device that is used to open or close a circuit.
• Safety is important while using electricity.