1) Electromagnetic induction is not used in , March 2006 (A) room heater (B) transformer (C) choke coil. (D) A.C.generator Correct Answer :room heater 2) In television, blanking pulse is applied to , March 2006 (A) control grid (B) filament. (C) horizontal plates  (D) vertical plates Correct Answer :control grid 3) The time taken by the radioactive element to reduce to $\displaystyle\frac{{1}}{{e}}$ times is , March 2006 (A)$\displaystyle\frac{{{h}{a}{l}{f{-}}{l}{\quad\text{if}\quad}{e}}}{{2}}$ (B) twice the mean life. (C) mean life (D) half-life Correct Answer :mean life 4) In LCR series a.c. circuit, the phase difference between current and voltage is 30$\displaystyle\circ$ . The reactance of the circuit is 17.32 $\displaystyle\Omega$ . The value of resistance is , June 2006 (A)1.732 $\displaystyle\Omega$ (B) 10 $\displaystyle\Omega$ (C) 17.32 $\displaystyle\Omega$ (D) 30 $\displaystyle\Omega$ Correct Answer :30 $\displaystyle\Omega$ 5) Potential energy of two equal negative point charges of magnitude 2 $\displaystyle\mu$C placed 1 m apart in air is , June 2006 (A)2 J (B) 0.036 J (C) 0.36 J (D) 4 J Correct Answer :0.036 J 6) In an AM superheterodyne receiver, the local oscillator frequency is 1.245 MHz. The tuned station frequency is , June 2006 (A) 990 kHz (B) 790 kHz (C) 455 kHz (D) 690 kHz Correct Answer :790 kHz 7) In an a.c. circuit, the current $\displaystyle{I}$ = $\displaystyle{I}_{{0}}$ sin $\displaystyle{\left(\omega{t}-\frac{\pi}{{2}}\right)}$ lags behind the e.m.f.e = $\displaystyle{E}_{{0}}$ sin $\displaystyle{\left(\omega{t}+\frac{\pi}{{2}}\right)}$by , September 2006 (A) $\displaystyle\frac{\pi}{{4}}$ (B) $\displaystyle\frac{\pi}{{2}}$ (C) 0 (D) $\displaystyle\pi$ Correct Answer :$\displaystyle\pi$ 8. A ray of light passes from a denser medium into a rarer medium. For an angle of incidence of 45$\displaystyle\circ$ , the refracted ray grazes the surface of separation of the two media. The refractive index of the denser medium is , September 2006 (A)$\displaystyle\frac{{3}}{{2}}$ (B)$\displaystyle\sqrt{{{2}}}$ (C) 2. (D) $\displaystyle\frac{{{1}}}{\sqrt{{{2}}}}$ Correct Answer :$\displaystyle\sqrt{{{2}}}$ 9) According to special theory of relativity the only constant in all frames is , September 2006 (A) mass (B) time (C) length (D) velocity of light Correct Answer :velocity of light