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Give Two Examples of Substances Which Are Good Conductors of Electricity. Why Do You Think They Are Good Conductors of Electricity? - Science

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प्रश्न

 Give two examples of substances which are good conductors of electricity. Why do you think they are good conductors of electricity?

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उत्तर

Copper and aluminium are good conductors of electricity because their resistivity is very low.

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पाठ 1: Electricity - Exercise 4

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संबंधित प्रश्‍न

A copper wire has diameter 0.5 mm and resistivity of 1.6 × 10−8Ω m. What will be the length of this wire to make its resistance 10 Ω? How much does the resistance change if the diameter is doubled?


Why are alloys commonly used in electrical heating devices? Give reason.


Fill in the following blanks with suitable words: 

Copper is a good .......... Plastic is an ..........


What is meant by conductors and insulators? Give two examples of conductors and two of insulators.


 What is meant by the "resistance of a conductor" ? Write the relation between resistance, potential difference and current.


 What happens to the resistance as the conductor is made thinner?


What happens to the resistance as the conductor is made thicker?


What will be the resistance of a metal wire of length 2 metres and area of cross-section 1.55 × 10−6 m2 if the resistivity of the metal be 2.8 × 10−8 Ω m?


Calculate the resistance of a copper wire 1.0 km long and 0.50 mm diameter if the resistivity of copper is 1.7 × 10−8 Ω m.


How does the resistance of a conductor depend on: 

 temperature of the conductor?


What would be the effect on the resistance of a metal wire of:

increasing its length?


What would be the effect on the resistance of a metal wire of:  

increasing its temperature?

 


Write the relation between resistance and electrical resistivity of the material of a conductor in the shape of a cylinder of length `'l'`  and area of cross-section `'A'` . Hence derive the S.I. unit of electrical resistivity.


How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistors R1, R2 and R3 in series connected to a battery of V volts?


Materials which allow larger currents to flow through them are called:


Use the data in the Table given below to answer the following –

Which material is the best conductor?

Table give below Electrical resistivity of some substances at 20°C

Electrical resistivity of some substances at 20°C
Material Resistivity (Ω m)
Conductors








Silver 1.60 × 10−8
Copper 1.62 × 10−8
Aluminium 2.63 × 10−8
Tungsten 5.20 × 10−8
Nickel 6.84 × 10−8
Iron 10.0 × 10−8
Chromium 12.9 × 10−8
Mercury 94.0 × 10−8
Manganese 1.84 × 10−6
Alloys


Constantan
(alloy of Cu and Ni)
49 × 10−6
Manganin
(alloy of Cu, Mn and Ni)
44 × 10−6
Nichrome
(alloy of Ni, Cr, Mn and Fe)
100 × 10−6
Insulators Glass 1010 − 1014
Hard rubber 1013 − 1016
Ebonite 1015 − 1017
Diamond 1012 − 1013
Paper (dry) 1012

How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?


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