Join now for JEE/NEET and also prepare for Boards Learn Science & Maths Concepts for JEE, NEET, CBSE @ Rs. 99! Register Now
Hey there! We receieved your request
Stay Tuned as we are going to contact you within 1 Hour
One of our academic counsellors will contact you within 1 working day.
Click to Chat
1800-5470-145
+91 7353221155
CART 0
Use Coupon: CART20 and get 20% off on all online Study Material
Welcome User
OR
LOGIN
Complete Your Registration (Step 2 of 2 )
Sit and relax as our customer representative will contact you within 1 business day
OTP to be sent to Change
We have already discussed the concept of resistivity in detail in the earlier sections. The concepts of resistance and resistivity are quite interrelated. While resistance as the name suggests, measures how much a material obstructs the flow of current through it. Resistance is measured in ohms. Mathematically, it can be formulated by the formula E= I x R, where R is the resistance of the object, I is the electric current flowing through it and E is the amount of voltage applied across the object.
Resistivity is a slightly different concept from resistance. Resistivity is the amount of resistance present or exhibited by a material having specific or standard dimensions. Hence, we may define the resistivity of a material to be the resistance offered by a piece of material of length one meter and cross-sectional area of one square meter.
Both resistance and resistivity depend on temperature, but the only difference is that the dependence is linear for relatively small temperature changes while for big changes, the dependence is non-linear.
The attributes like shape or the cross-sectional area have an impact on the resistance of the conductor, but resistivity is not affected by it. Resistivity is only affected by the change in temperature. The relationship between resistivity and temperature is Δρ = α * ΔT * ρ_{0} Where: Δρ : Change of the resistivity α : Resistivity, temperature coefficient ΔT : Change of temperature ρ_{0} : Original resistivity For example, at 20 °C (293 K), the resistivity of Copper at 20 °C is 1.68 * 10^{-8} , it's temperature coefficient is 0.0039 K^{-1}, its resistivity at 30 °C is 1.75E-8.
Watch this Video for more reference
As stated above, the resistivity ‘r’ of a conductor is unaffected by its shape and size but is affected by its temperature. Increase in temperature results in an increase in ‘r’ especially in the case of Ohmic conductors. If the given temperature is denoted by ‘T’ then the expression for ‘r’ is:
r_{(t)} = r_{0} (1 + a DT), where r_{0} = resistivity at 0^{o}C,
a = temperature coefficient of resistivity.
Also, a = (p – p_{0}) / p_{0}ΔT or
a = 1 / p dp / dT.
For conductors ‘a’ is a positive constant but for insulators and semiconductors it is negative.
We have tabulated below the values of resistivity of certain metals. It will provide you a clear idea of the effect of temperature on resistivity of metals.
Metal
Resistivity (Ω . m) at 20 °C
Temperature coefficient [K^{-1}]
Silver
1.59 × 10^{-8}
0.0038
Copper
1.68 × 10^{-8}
0.0039
Gold
2.44 × 10^{-8}
0.0034
Aluminium
2.82 × 10^{-8}
Calcium
3.36 × 10^{-8}
Tungsten
5.60 × 10^{-8}
0.0045
Zinc
5.90 × 10^{-8}
0.0037
Nickel
6.99 × 10^{-8}
0.006
Iron
1.0 × 10^{-7}
0.005
Platinum
1.06 × 10^{-7}
0.00392
Tin
1.09 × 10^{-7}
Lead
2.2 × 10^{-7}
Manganin
4.82 × 10^{-7}
0.000002
Constantan
4.9 × 10^{-7}
0.000008
Mercury
9.8 × 10^{-7}
0.0009
Nichrome
1.10 × 10^{-6}
0.0004
Carbon
3.5 × 10^{-5}
-0.0005
Germanium
4.6 × 10^{-1}
-0.048
Silicon
6.40 × 10^{2}
-0.075
Besides metals, we list below certain insulators with their resistivity:
P.V.C. 5.4 x 10^{15}
Glass 10^{4}
Quartz 10^{12}
P.T.F.E 10^{12}
Here, P.T.F.E stands for polytetrafluoroethylene which is used for the insulation of high voltage cables. The values in the above table clearly show that the resistivity of insulators is much higher than that of conductors.
askIITians offers comprehensive study material which covers the entire syllabus of IIT JEE in detail. All the important topics like variation of free energy using emf with temperature or studying the variation in resistance of conductor with temperature have also been included in the material. The aspirants must have agood hold on the topic in order to remain competitive in the JEE.
Click here for the Complete Syllabus of IIT JEE Physics.
Look into the Model Papers with Solutions to get a hint of the kinds of questions asked in the exam.
You can get the knowledge of Important Books of Physics here.
To read more, Buy study materials of Current Electricity comprising study notes, revision notes, video lectures, previous year solved questions etc. Also browse for more study materials on Physics here.
Get your questions answered by the expert for free
You will get reply from our expert in sometime.
We will notify you when Our expert answers your question. To View your Question
Resistance and Resistivity Table of Content...
Basic Concepts In electrostatics we have seen that...
Electrical Energy and Power Table of contents...
Mechanism of current flow in a metallic conductor...
Cells, EMF, Internal Resistance Table of Content...
Electric Current and Current Density Table of...
Meter Bridge Table of contents Wheatstone Bridge...
Specific Resistance of the Material of a wire...
Maximum Power Transfer Theorem Table of Content...
Combination of Resistors – Series and...
Grouping of Identical Cells Series Grouping E.m.f....
Int Introduction of Current Electricity Table of...
Drift of Electrons and the Origin of Resistivity...
Emf and Grouping of cells Table of Content...
Resistivity of Various Materials Table of contents...
Drift Velocity The average velocity attained by...
Temperature Dependence of Resistivity Table of...
Wheatstone Bridge Table of contents Introduction...
Solved Examples of Comlicated Circuits...
Kirchhoff’s Law Table of contents Current...
Potentiometer Table of contents Potentiometer and...
Thermal and Chemical Effect of current Table of...
Ohm’s Law Table of contents Voltage, Current...
Constant Potential Difference Table of Content...
Complicated Circuits As the name suggests,...
Errors The major systematic errors in this...
Cells in Series and in Parallel Table of Content...
Effective Grouping of Cells The flow of current...
Limitations of Ohm’s Law Table of contents...
Measurement of an unknown resistance using a Post...