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13. (a) List the factors on which the resistance of a conductor in the shape of a wire depends.
(b) Why are metals good conductors of electricity whereas glass is a bad conductor of electricity ?
Give reason
(c) Why are alloys commonly used in electrical heating devices ? Give reason.
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Answers
1.
resistance of a wire depends on P.D,physical conditions such as temp.
2.
there are so because they have free electrons in them
3.
alloys are generally used in heating devices since alloys have low melting point thus producing resistance and becoming hot.
(a) Factors on which the resistance of a conductor in the shape of a wire depends are:
- Length of the wire
- Cross section area of the wire
- Nature of the material of the wire
- Resistance also depends on temperature
(b) Metals are good conductor of electricity because they have very large number of free valance electrons whereas glass has no free electrons to conduct electricity. So metals good conductor whereas glass is a bad conductor of electricity
(c) Alloys are materials that have both the properties of conductor as well as insulator.
Alloys are used instead of a pure metal in the electrical heating devices because they have the less electrical conductivity and low melting point. That's why alloys are commonly used in electrical heating devices