Q.1. Select the best option/answer and fill in the appropriate box on the Answer Sheet. (20)

(i) A Watt – sec is a unit of:
(a) Force
(b) Energy
(c) Power
(d) None of these

(ii) The direction of any magnetic induction effect is such as to oppose the cause of the effect. This is:
(a) Coulumb's Law
(b) Ampere's Law
(c) Lenz's Law
(d) None of these

(iii) A magnetic field cannot:
(a) accelerate a charge
(b) Exert a force on a charge
(c) change the kinetic energy of a charge
(d) None of these ( F=q v x b )

(iv) The inverse of resistivity is called Conductivity. Its unit is:
(a) Ohm-1
(b) ohm-metre
(c) (ohm-meter)-1
(d) None of these

(v) An LRC Circuit has R= 4Ω, Xc = 3 and XL=6, the impedence of the circuit is:
(a) 5 Ω
(b) 7 Ω
(c) 13 Ω
(d) None of these

(vi) A "step-down" transformer is used to:
(a) increase the power
(b) decrease the voltage
(c) Increase the voltage
(d) None of these

(vii) Electrical potential is the potential energy per unit:
(a) Charge
(b) Voltage
(c) Force
(d) None of these

(viii) The force on a charge moving with the velocity in a magnetic field B is given by:
(a) F = (q/v x B)
(b) F = ( qv x B )
(c) F = (qv + B)
(d) None of these

(ix) A changing current "i" in any circuit induces an emf "e" in that circuit, which is equal to:
(a) e = di/dt
(b) E = i dΦ/dt
(c) e = - L di/dt
(d) None of these

(x) Inductive reactance of an inductor is:
(a) XL= ω2L
(b) XL = ω/L
(c) e = -L di/dt
(d) None of these (XL = ω.L )

(xi) The resonant frequency of an LC-Circuit is:
(a) f = 2Π LC
(b) f = 1 / 2Π√ LC
(c) f = 1/ 2LC
(d) None of these

(xii) The deliberate addition of an impurity element in a semi-conductor is called:
(a) doping
(b) annealing
(c) mixing
(d) None of these

(xiii) The conversion of AC into DC is called:
(a) amplification
(b) rectification
(c) modulation
(d) None of these

(xiv) The Laser light is:
(a) monochromatic
(b) coloured
(c) chromatic
(d) None of these

(xv) The Laser light may be obtained from:
(a) quartz crystal
(b) NaCl crystal
(c) ruby crystal
(d) None of these

(xvi) The emission of photoelectrons in photoelectric effect is dependent on:
(a) threshold frequency
(b) intensity of light
(c) Nature of metal
(d) None of these

(xvii) Which one of the following is NOT needed in Nuclear Fission reactor:
(a) fuel
(b) accelerator
(c) moderator
(d) None of these

(xviii) The half life of a radioactive isotope is 140 days. How many days would it take to loose 3/4 of its initial activities:
(a) 105 days
(b) 280 days
(c) 35 days
(d) None of these

(xix) Most of the energy produced in Sun is due to:
(a) Nuclear fusion
(b) Chemical reaction
(c) Nuclear Fission
(d) None of these

(xx) A U-235 nucleus will split when it captures:
(a) an α-particle
(b) e.m. radiation
(c) neutron
(d) None of these