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Home/class 12 chapter-3 physics/Page 2

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Ashok0210
Ashok0210
Asked: February 23, 2021In: Class 12 Physics

Choose the correct alternative: (a) Alloys of metals usually have (greater/less) resistivity than that of their constituent metals. (b) Alloys usually have much (lower/higher) temperature coefficients of resistance than pure metals. (c) The resistivity of the alloy manganin is nearly independent of/ increases rapidly with increase of temperature. (d) The resistivity of a typical insulator (e.g., amber) is greater than that of a metal by a factor of the order of (10²²/10³ ).

Class 12 Physics CBSE and UP Board Current Electricity Additional Exercise Chapter-3 Exercise 3.19 NCERT Solutions Class 12 Physics Chapter 3 Question 19

2020-2021cbse and up boardclass 12 chapter-3 physicsclass 12 physicsncert class 12 current electricity
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Ashok0210
Ashok0210
Asked: February 23, 2021In: Class 12 Physics

Answer the following questions: (a) A steady current flows in a metallic conductor of non-uniform cross-section. Which of these quantities is constant along the conductor: current, current density, electric field, drift speed? (b) Is Ohm’s law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm’s law. (c) A low voltage supply from which one needs high currents must have very low internal resistance. Why? (d) A high tension (HT) supply of, say, 6 kV must have a very large internal resistance. Why?

Class 12 Physics CBSE and UP Board Current Electricity Additional Exercise Chapter-3 Exercise 3.18 NCERT Solutions Class 12 Physics Chapter 3 Question 18

2020-2021cbse and up boardclass 12 chapter-3 physicsclass 12 physicsncert class 12 current electricity
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Ashok0210
Ashok0210
Asked: February 23, 2021In: Class 12 Physics

What conclusion can you draw from the following observations on a resistor made of alloy manganin?

What conclusion can you draw from the following observations on a resistor made of alloy manganin?

Class 12 Physics CBSE and UP Board Current Electricity Additional Exercise Chapter-3 Exercise 3.17 NCERT Solutions Class 12 Physics Chapter 3 Question 17

2020-2021cbse and up boardclass 12 chapter-3 physicsclass 12 physicsncert class 12 current electricity
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Ashok0210
Ashok0210
Asked: February 23, 2021In: Class 12 Physics

Two wires of equal length, one of aluminum and the other of copper have the same resistance. Which of the two wires is lighter? Hence explain why aluminum wires are preferred for overhead power cables. (ρAl = 2.63 × 10⁻⁸ Ω m, ρCu = 1.72 × 10⁻⁸Ω m, Relative density of Al = 2.7, of Cu = 8.9.)

Class 12 Physics CBSE and UP Board Current Electricity Additional Exercise Chapter-3 Exercise 3.16 NCERT Solutions Class 12 Physics Chapter 3 Question 16

2020-2021cbse and up boardclass 12 chapter-3 physicsclass 12 physicsncert class 12 current electricity
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Ashok0210
Ashok0210
Asked: February 23, 2021In: Class 12 Physics

(a) Six lead-acid type of secondary cells each of emf 2.0 V and internal resistance 0.015 Ω are joined in series to provide a supply to a resistance of 8.5 Ω. What are the current drawn from the supply and its terminal voltage? (b) A secondary cell after long use has an emf of 1.9 V and a large internal resistance of 380 Ω. What maximum current can be drawn from the cell? Could the cell drive the starting motor of a car?

Class 12 Physics CBSE and UP Board Current Electricity Additional Exercise Chapter-3 Exercise 3.15 NCERT Solutions Class 12 Physics Chapter 3 Question 15

2020-2021cbse and up boardclass 12 chapter-3 physicsclass 12 physicsncert class 12 current electricity
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