MASTERMIND TUTORIAL

BY SANTOSH TIWARY EXAMINATION PAPERS

2008 DELHI SET -1

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ALL INDIA SET -1

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2009DELHI SET -1

ALL INDIASET -1

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2. A steady current flows in a metallic conductor of non-uniform cross-section. Which of thesequantities is constant along the conductor:Current, current density, drift speed, electric field? 1

2010DELHI SET -17. A wire of resistance 8 R is bent in the form of a circle. What is theeffective resistance between the ends of a diameter AB ?

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20. In a metre bridge, the null point is found at a distance of l1 cm from A. If now a resistance of X isconnected in parallel with S, the null point occurs at l2 cm. Obtain a formula for X in terms ofl1, l2 and S.

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6. Two conducting wires X and Y of same diameter but different materials are joined in series acrossa battery. If the number density of electrons in X is twice that in Y, find the ratio of drift velocityof electrons in the two wires.

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FOREIGNSET -1

15. State the principle of working of a potentiometer. Define potential

gradient and write its S.I. unit.

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2011DELHI SET -13. A resistance R is connected across a cell of emf and internal resistance r. A potentiometer nowmeasures the potential difference between the terminals of the cell as V. Write the expression for‘r’ in terms of , V and R.

19. Define the terms (i) drift velocity, (ii) relaxation time.A conductor of length L is connected to a dc source of emf . If this conductor is replaced byanother conductor of same material and same area of cross-section but of length 3L, how will thedrift velocity change?

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18. In the meter bridge experiment, balance point was observed at J with AJ = l.

27. Two heating elements of resistance R1 and R2 when operated at a constant supply of voltage, V,consume powers P1 and P2 respectively. Deduce the expressions for the power of theircombination when they are, in turn, connected in (i) series and (ii) parallel across the same voltagesupply

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FOREIGN

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2012DELHI

SET -11. When electrons drift in a metal from lower to higher potential, does it mean that all the freeelectrons of the metal are moving in the same direction?

3. Show on a graph, the variation of resistivity with temperature for a typical semiconductor.

11. A cell of emf E and internal resistance r is connected to two external resistances R1 and R2 and aperfect ammeter. The current in the circuit is measured in four different situations:(i) without any external resistance in the circuit.(ii) with resistance R1 only(iii) with R1 and R2 in series combination(iv) with R1 and R2 in parallel combination.The currents measured in the four cases are 0.42 A, 1.05 A, 1.4 A and 4.2 A, but not necessarily inthat order. Identify the currents corresponding to the four cases mentioned above

ALL INDIASET -1 1. Two wires of equal length, one of copper and the other of manganin have the same resistance.Which wire is thicker?

17. A light bulb is rated 100 W for 220 V ac supply of 50 Hz. Calculate(i) the resistance of the bulb;(ii) the rms current through the bulb

ORAn alternating voltage given by V = 140 sin 314 t is connected across a pure resistor of 50 . Find(i) the frequency of the source.(ii) the rms current through the resistor.

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2013DELHI

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1. A cell of emf ‘E’ and internal resistance ‘r’ draws a current ‘I’. Write the relation between terminalvoltage ‘V’ in terms of E, I and r.

3. A heating element is marked 210 V, 630 W. What is the value of the current drawn by the elementwhen connected to a 210 V dc source?

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ALL INDIA

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13. Explain the term ‘drift velocity’ of electrons in a conductor. Hence obtain the expression for thecurrent through a conductor in terms of ‘drift velocity’.ORDescribe briefly, with the help of a circuit diagram, how a potentiometer is used to determine theinternal resistance of a cell.

FOREIGN

SET -1 6. Plot a graph showing the variation of resistance of a conducting wire as a function of its radius,keeping the length of the wire and its temperature as constant.7. Two materials Si and Cu, are cooled from 300 K to 60 K. What will be the effect on their resistivity?

22. (a) State, with the help of a suitable diagram, the principle on which the working of a meter bridgeis based.(b) Answer the following:(i) Why are the connections between resistors in a meter bridge made of thick copper strips?(ii) Why is it generally preferred to obtain the balance point near the middle of the bridge

wire in meter bridge experiments?

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5. Two materials, Ge and Al, are cooled from 300K to 60 K. What will be the effect on their resistivity?

SET-34. Two materials, Ag and GaAs, are cooled from 300 K to 60 K. What will be the effect on theresistivity?

2014DELHISET -11. Define the term ‘Mobility’ of charge carries in a conductor. Write its SI unit.

5. Show variation of resistivity of copper as a function of temperature in a graph.

13. State Kirchhoff’s rules. Explain briefly how these rules are justified

21. A potentiometer wire of length 1 m has a resistance of 10 . It is connected to a 6 V battery in serieswith a resistance of 5 . Determine the emf of the primary cell which gives a balance point at 40 cm.

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1. Define the term ‘electrical conductivity’ of a metallic wire. Write its S.I. unit.

3. Show variation of resistivity of Si with temperature in a graph.

24. A potentiometer wire of length 1.0 m has a resistance of 15 . It is connected to a 5 V battery in serieswith a resistance of 5 . Determine the emf of the primary cell which gives a balance point at 60 cm.

SET-31. Define the term ‘drift velocity’ of charge carriers in a conductor and write its relationship with thecurrent flowing through it.

4. Plot a graph showing variation of current versus voltage for the material GaAs.

25. A potentiometer wire of length 1 m has a resistance of 5 . It is connected to a 8 V battery in serieswith a resistance of 15 . Determine the emf of the primary cell which gives a balance point at 60 cm.

ALL INDIA

SET -112. A cell of emf ‘E’ and internal resistance ‘r’ is connected across a variable resistor ‘R’. Plot a graphshowing variation of terminal voltage ‘V’ of the cell versus the current ‘I’. Using the plot, show howthe emf of the cell and its internal resistance can be determined

14. Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 1.0 ×10–7 m2 carrying a current of 1.5 A. Assume the density of conduction electrons to be 9 1028 m–3.

S9. Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 2.5 ×10–7 m2 carrying a current of 1.8 A. Assume the density of conduction electrons to be 9 × 1028 m–3

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10. Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area2.5 × 10–7 m2 carrying a current of 2.7 A. Assume the density of conduction electrons to be9 × 1028 m–3.

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