15. A simple LR circuit is connected to a battery at t = 0. The time instant at which rate of energy storage in inductor is half of power delivered by battery (a) In 2 (c) In 2 (b) In () (d) In 3 16. A uniform rod, of mass m, length I and r radius of cross section, is rotated about an axis passing through one of its ends and perpendicular to its length with constant angular velocity w in horizontal plane. If Y is the Young's modulus of the material of rod, the increase in its length due to rotation of rod is (a) ry (c) 3 (b) mw 2mry 2mw ry 17. A free particle having one electronic charge with initial kinetic energy 9 eV and de Broglie wavelength 1 mm enters a region of Vo potential difference such that new de Broglie wavelength is now 1.5 mm. Then eV, is (a) 5 eV (c) 13.5 eV (b) 6 eV Yshike (d) 15 eV 18. A radioactive in 2nd by 2 -emission. A detector records n-particles (accumulatively) it records 1.1 n -particle. Number of -particles recorded by detector after a long time, is 1in 10 (c) 2n (b) (d) 12n 10n 9