Question

interesying qiestion and hard

Answer 1

Resistance depends on

1. Cross section area I.e R is inversely proportional to A

2. Length is directly proportional to R

3. Nature of a material

Metals are good conductors because they have ions which facilities the flow of current

Alloys are commonly used in electectrical heating device as they have high melting point

Answer 2

a) The resistance depends on two factors when we talk about the shape of the wire

1) resistance is directly proportional to the length of the wire.
2) resistance is inversely proportional to the area of the cross section of the wire.

b) Metals have low resistivity thus they provide very low resistance to the flow of charges i.e they allow the current to flow very easily.
However the resistivity of glass is very high.
Hence it provides a lot of resistance to the flow of charge.
And hence glass is a bad conductor of electricity and metals are good conductors of electricity.

c) The resistivity of alloys is higher than the resistivity of pure metal.
Hence the alloys like nichrome provide a lot of resistance to the flow of current.
This power loss generates a lot of heat energy.
Hence alloys are used for making electrical appliances.