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Category: Class 12

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Ashok0210

Asked: February 23, 2021In: Class 12 Physics

(a) Given n resistors each of resistance R, how will you combine them to get the (i) maximum (ii) minimum effective resistance? What is the ratio of the maximum to minimum resistance? (b) Given the resistances of 1 Ω, 2 Ω, 3 Ω, how will be combine them to get an equivalent resistance of (i) (11/3) Ω (ii) (11/5) Ω, (iii) 6 Ω, (iv) (6/11) Ω? (c) Determine the equivalent resistance of networks shown in Fig. 3.31.

Class 12 Physics CBSE and UP Board Current Electricity Additional Exercise Chapter-3 Exercise 3.20 NCERT Solutions Class 12 Physics Chapter 3 Question 20

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

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

Ashok0210

Asked: February 23, 2021In: Class 12 Physics

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

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

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Category: Class 12

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

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