May 2011 - Career Point

Physics Challenging ProblemsSet # 1This section is designed to give IIT JEE aspirants a thorough grinding & exposure to varietyof possible twists and turns of problems in physics that would be very helpful in facing IITJEE. Each and every problem is well thought of in order to strengthen the concepts and wehope that this section would prove a rich resource for practicing challenging problems andenhancing the preparation level of IIT JEE aspirants.By : Dev SharmaSolutions available in next issueDirector Academics, Jodhpur Branch1. A thin rod of length 2L is placed horizontally in adown ward uniform electric field E. Half of lengthis charged positively and other half with linearcharge density λ . The rod of is hinged at its middlepoint and free to rotate in vertical plane, A weight wis hanged at a distance x from hinge to keep ithorizontal. The value of x isEλλ– – – – – – + + + + + + +O(A)(C)wλEEλL2wwx2LEλL2(B)2w(D)22EλLw2. S is a cross section of a solenoid where magneticfields is increasing at a constant positive rate. V 1 andV 2 are two ideal voltmeters, then V 1 /V 2 isV 1 1Ω× ×× ×× × ×2Ω V 2S(A) 1 (B) 0.5(C) 2 (D) 0.25Passage # 1 (Q. No. 3 to Q. No. 4)In the given circuits three inductors L 1 , L 2 and L 3and a resistance R are connected to a V volt batteryneglecting mutual inductance. At t = 0 switch isclosed and L 3 > L 2 > L 1 .L 2L 3 L 13. Find current through L 1 will beV L2(A)R L1+ L2+ L3V L1(B)R L1+ L2+ L3V L3(C)R L1+ L2+ L3(D)Can’t be determined4. Time constant of the circuit is :(A)(C)L1 + L2+ L3R⎛R⎜⎝1L1+L1+2 1 L3⎞⎟⎠V(B)⎛⎜⎝1LR1R+L1+3 1 L2(D) None of thesePassage # 2 (Q. No. 5 to Q. No. 6)Hydrogen gas in the atomic state is excited to aenergy level such that the electrostatic potentialenergy of H-atom becomes -1.7eV. Now aphotoelectric plate having work function W = 2.3eVis exposed to the emission spectra of this gas.Assuming all transitions to be possible. Answer thefollowing questions.⎞⎟⎠XtraEdge for IIT-JEE 14 MAY 2011