A fresh set of 20 random questions is generated every time you open this page and every time you refresh it.For each of the following multiple choice questions, choose the most appropriate answer :
1. The minimnm potential difference between the base and emitter reqnired to swltch a silicon transistor ‘ON’ is approximately
A. 1 V
B. 3V
C. 5V
D. 4.2V
2. The ground state energy of hydrogen atom is - 13.6 eV. What is the potential energy of the electron in this state ?
A. 0 eV
B. -27.2 eV
C. 2 eV
D. 1 eV
3. An astronaut is looking down on earth's surface from a space shuttle at an altitude of 400 km. Assuming that the astronaut's pupil diameter is 5 mm and the wavelength of visible light is 500 nm, the astronaut will be able to resolve linear objects of the size of about
A. 10.5m
B. 25m
C. 50m
D. 500m
4. A light signal photon cannot escape from the surface of a
A. neutron star
B. black hole
C. red giant
D. white dwarf
5. A child is swinging a swing. Minimum and maximum heights of swing from earth’s surface are 0.75 m and 2m respectively. The maximum velocity of this swing is?
A. 5 m/s
B. 10 m/s
C. 15 m/s
D. 20 m/s
6. Shadows consist of two portions, the umbra and the penumbra. Which statement below applies ONLY to the umbra?
A. lt receives no light from any part of the source
B. lt receives light from part of the source
C. lt is a partial shadow
D. It is circular in shape
7. When an electron positron pair annihilates, the energy released is about
A. 0.8E-13 J
B. 1.6E-13
C. 3.2E-13 J
D. 4.8E-13 J
8. When analyzed, most complicated machines are found to consist of a combination of various simple machines. Which machine below is NOT a simple machine ?
A. lever
B. electric motor
C. inclined plane
D. pulley
9. A person suffering from hypermetropia requires which type of spectacle lenses
A. Convex lens
B. Convex-concave lens
C. Plano-concave lens
D. Concave lens
10. A double slit experiment is performed with light of wavelength 500 nm. A thin film of thickness 2 ?m and refractive index 1.5 is introduced in the path of the upper beam. The location of the central maximum will
A. Remain unshifted
B. Shift downward by nearly two fringes
C. Shift upward by nearly two fringes
D. Shift downward by 10 fringes
11. A sphere of mass M and radius R is falling in a viscous fluid. The terminal velocity attained by the falling object will be proportional to
A. R x R
B. R
C. 1/R
D. 1/R/R
12. An earthquake generates both transverse S and longitudinal P sound waves in the earth . The speed of S waves is about 4.5 km/s and that of P waves is about 8.0 km/s. A seismograph records P and S waves from an earthquake . The first P wave arrives 4.0 min before the first S wave. The epicenter oi the earthquake is located at a distance of about
A. 25 km
B. 250 km
C. 2500 km
D. 500km
13. An electric fan has blades of length 30 cm measured from the axis of rotation. If the fan is rotating at 120 rpm, the acceleration of a point on the tip of the blade is ?
A. 1600 m/s/s
B. 47.4 m/s/s
C. 23.7 m/s/s
D. 50.55 m/s/s
14. lf the density of a given body is 10 gm/cms, what is its specific gravity ?
A. 0.01
B. 1.0
C. 1.0
D. 10.0
15. Characteristic X-rays are produced due to
A. Transfer of momentum in collision of electrons with target atoms
B. Transition of electrons from higher to lower electronic orbits in an atom
C. Heating of the target
D. Transfer of energy in collision Ef electrons with atoms in the target
16. The specific charge of an electron is
A. 5.7E7 Coulomb/kg
B. 1.76E11 Coulomb/kg
C. 1.6E-19 Coulomb/gm
D. 1.6E-19 Coulomb
17. The velocity with which a projectile must be fired so that it escapes earth's gravitation does not depend on
A. Mass of the earth A
B. Mass of the projectile
C. Radius of the projectile's orbit
D. Gravitational constant
18. A wire of length L is drawn such that its diameter is reduced to half of its original diameter. If the initial resistance of the wire is 10 ohms, its new resistance would be
A. 40 ohms
B. 80 ohms
C. 120 ohms
D. 160 ohms
19. When milk is churned, cream gets separated due to ?
A. centripetal force
B. centrifugal force
C. frictional force
D. gravitational force
20. A stone of mass m is tied to a string of length l and rotated in a circle with a constant speed v. If the string is released, the stone flies
A. Tangential outward
B. Radically outward
C. Radially inward
D. With an acceleration mv2/l
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