Conductors and insulators - class-VII

Out of eraser, paper, copper wire, and polythene, only copper wire is the conductor which is used in the conduction and are used in many practical application circuit.

Glass wool is an insulating material made from fibres of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in the thermal insulation properties.
Glass wool is produced in rolls or in slabs, with different thermal and mechanical properties. It may also be produced as a material that can be sprayed or applied in place, on the surface to be insulated.
They possess very low expansion property, remarkable thermal shock resistance, low thermal conductivity, excellent electrical insulation up to 1000 C, and excellent resistance to corrosion from molten metal. 
Hence, Glass wool is a poor conductor of electricity.

The electrical conductivity of matter is dependent upon the atomic structure of the material from which the conductor is made. In any solid material, such as copper, the atoms which make up the molecular structure are bound firmly together. At room temperature, copper will contain a considerable amount of heat energy. Since heat energy is one method of removing electrons from their orbits, copper will contain many free electrons that can move from atom to atom. When not under the influence of an external force, these electrons move in a zigzag manner within the conductor. This movement is equal in all directions so that electrons are not lost or gained by any part of the conductor. When controlled by an external force, the electrons move generally in the same direction. The effect of this movement is felt almost instantly from one end of the conductor to the other. This electron movement is called an ELECTRIC CURRENT.
Some metals are better conductors of electricity than others. Silver, copper, gold, and aluminum are materials with many free electrons and make good conductors. Silver is the best conductor, followed by copper, gold, and aluminum. Copper is used more often than silver because of cost. Aluminum is used where weight is a major consideration, such as in high-tension power lines, with long spans between supports. Gold is used where oxidation or corrosion is a consideration and a good conductivity is required.
Hence, Aluminium is a good conductor of electricity.

The electrical and thermal conduction properties of a material can be similar or very different, in metals the electrical and thermal conductivity is due to free electrons, in non-metals thermal conductivity has nothing to do with free electrons, but more to do with lattice vibrations (that is, phonons). 
So mica has good thermal conductivity due to phonons, but doesn't have sufficient free electrons and a very high resistance to be a good conductor of electricity.
Hence, Mica is a poor or bad conductor of electricity.

Plastic is a good insulator of electricity and makes it possible to work with wires without any harm or injury.

Metals are good conductors of electricity.
Silver is a metal and a good conductor of electricity.

Metals are generally good conductors of electricity. So, Gold and Aluminium are good conductors of electricity. 
Non-metals are poor conductors of electricity.
So rubber, being a non-metal, is an electrical insulator and hence a poor conductor of electricity.

For bulb to glow there should be current passing through it's entire circuit. But when probs are hanged in the air the circuit breaks as air do not conduct electricity (or bad conductor of electricity). 

Metals have loosely bound outer electrons that is they have charge carriers which can move easily (current) when a potential difference is applied. Therefore, these loosely bound outer electrons make metals good conductors. 

Iron and Silver are metals so they are conductors. While carbon is conductor in graphite and insulator in diamond form. So only option left is wood which an insulator.  

Silver is a better conductor, non magnetic but expensive material compared to copper therefore copper is generally used for electrical wiring.

Some materials have electrons that are tightly bound to the nucleus and are not free to travel within the substance. These materials are called insulators.
An electrical insulator is a material whose internal electric charges do not flow freely, and therefore make it very hard to conduct an electric current under the influence of an electric field.

Answer is D.

Bakelite, or polyoxybenzylmethylenglycolanhydride, is an early plastic. It is a thermosetting phenol formaldehyde resin, formed from an elimination reaction of phenol with formaldehyde. It was developed by Belgian-born chemist Leo Baekeland in New York in 1907.
One of the first plastics made from synthetic components, Bakelite was used for its electrical nonconductivity and heat-resistant properties in electrical insulators, radio and telephone casings, and such diverse products as kitchenware, jewelry, pipe stems, firearms, and children's toys.
If the Bakelite is dry, it won't conduct electricity, however if it is wet and a high enough voltage is applied to it, it might conduct electricity.

Distilled water  is bad conductor of electricity.

The current does not flow through the insulators. We know that a large amount of current will flow through the conductor due to the presence of free electrons. Relatively small amount of current also flow through semiconductors or some alloys. 

In conductors electrons can flow because their because their electrons are free and mobile.

Metallic elements have free electrons on the metallic surface and thus they are extremely good conductors. 

The materials that do not allow flow of electron through them are known as Insulators.

True

Until the overall repulsive forces between electrons is minimised, the charged particle continues to transmit charge to other particles.

We know that a conductor has free electrons and due to this, the conductor is able to transfer electric charge (the current).  

Earthing means to connect electrical system to earth or soil in such a manner as it ensures an immediate discharge of electrical energy night out any danger. it is essentially done to product the building from any miss happening.

Ordinary rubber is an insulator. But the special rubber tyres of aircrafts are made slightly conducting. This is because during landing or takeoff, the tyres of aircrafts get charged due to friction between tyres and the ground. In such case, the tyres are slightly conducting, the charges developed on the tyres will not stay on them and find its way to earth.

Non-metals are the bad conductor of electricity except one i.e Graphite(made of carbon).Hence iodine,sulphur and bromine do not conduct electricity.

False.

False.

Out of the given options, ebonite is best insulator. Whereas, carbon and graphite are fair conductors and ebonite is a better insulator than paper.

Tap water conducts electricity since there are small amounts of calcium and magnesium salts dissolve in it, pure water (distilled or de-ionised) has nothing at all in it that can conduct electricity. This is because water itself isn't a conductor. However, when one dissolves ionic compound such as salts, the ions becomes loosely bound to each other which makes tap water a good conductor of electricity. 

Light emitting diodes are used in calculators.

Most solid materials are classified as insulators because they offer large resistance to the flow of electric current. because they do not have free electrons.

Insulators are the materials that do not allow free flow of electrons from atom to atom and molecule to molecule. Subsequently charge is seldom distributed evenly across the surface of an insulator while, insulators are not used for transferring a charge, they do serve a critical role in electrostatic experiments and demonstrations.

Lightening gets to the ground if the charges flow from lightening to the ground. It happens when these charges follow a path of least impedance. 

During discharging of a charged glass rod via earthing the connecting material should be such that it allows charge to flow through them easily. Such a material is a conductor. So, the connecting material can be a conducting wire. 

A charged glass rod can be discharged by connecting it to the ground (i.e, earthing it) via a conducting wire. In this way, charge from glass rod will flow to the ground via the conducting wire. 

At room temperature, conductivity is less because of obstruction from other ions.
At low pressure, this disturbance is reduced and hence gases become good conductors.