This is the correct option. The earth wire is a safety device to prevent electrocution and electric fires, especially in an electrical device with a metal frame or cover. 

Correct option. The chemicals stored in a cell that are the source of electricity in it. It is the mixture of manganese dioxide and carbon particles.

This is the correct option. Rubber is a insulator of electricity. It therefore does not allow electric current to pass. 

The complete path from one terminal of an electric cell through the bulb and back to the other terminal is called open circuit, and  is an incorrect statement. It is called an closed circuit.

This is the correct option. When the work is done upon the object, that object gains energy. The energy acquired by the objects upon which work is done is known as mechanical energy. The motor here converts the electric energy into mechanical energy.

This is the correct option. Nickel is a good conductor of electricity. A good conductor of electricity is a substance that allows electric current to flow through it with little resistance. Most metals are good conductors of electricity.

This is the correct option. Conductors allow the current to pass through them, graphite is a good conductor of electricity, insulators do not allow the current to pass through them and terminals are the ends of an electric cell.

This is the correct option as the statement is incorrect. An electric bulb is a device, which changes electric energy into light energy and not light energy into electric energy.

This is the correct option. A windmill does not uses electrical energy, rather it uses wind energy and converts it into electrical energy.

This is the correct option. The flow of current is from the positive terminal to the negative terminal. Only then it is called a complete circuit.

This is the correct option. The filament inside a light bulb is made of tungsten because it has an unusually high melting point. When electric current is passed through the filament, it gets white hot and produces light.

This is the correct option. When two or more cells are joined in such a way that the positive terminal of one cell is joined by the negative terminal of another cell, it is called a battery. Thus in a battery, the correct sequence is: positive - negative - positive - negative and so on.

This is the correct option. Electric energy is transformed into light energy in electric bulb, sound energy in loud-speaker, mechanical energy in electric motor and magnetic energy in electromagnets. 

This is the correct option. The electrical unit of measurement of voltage is volts and it is denoted by V.

This is the correct option. A resistor obstructs the flow of current, plug-key is used to close and open the circuit, connector is used to join battery and terminals and graphite is a non-metal that conducts electricity.