Download Ans: b

Dr. Amerjeet Singh Written Examination for Class X
1. When a body become negatively charged by rubbing, it means that it has
a. Acquires excess electron
c. Lost some electrons
b. Acquires excess proton
d. Lost some proton
Ans: a
2. If the potential difference across a resistor in a circuit is doubled , the current flowing through
it will be
a. Halved
Ans: b
b. Doubled
c. Tripled
d. Quadrupled
3. The direction of conventional current is
a. first from negative terminal to positive terminal and vice versa
b. First from positive terminal to negative terminal and vice versa
c. From negative terminal to positive terminal only
d. From positive terminal to negative terminal only
Ans: d
4. If the current passing through a conductor is doubled then heat produced will be
a. Four times the original heat
b. One fourth of the original heat
c. Remains the same
d. Half of the original heat
Ans: a
5. When two or more resistors are connected in parallel
a. The current through each resistor is same
b. The potential difference across each resistor is same
c. The current and the potential difference are inversely proportional
d. The current increases linearly
Ans: b
6. Cu and Al wires are used for electricity transmission because they
a. Have high resistance b. Are easily available c. Have low resistance d. Are of low cost
Ans: c
7. In ohms law experiment a dry cell is used to
a. Measure the potential difference
b. Measure the resistance of the conductor
c. Measure the current through the conductor
d. Maintain the potential difference between two points of the conductor
Ans: d
8. A copper wire of diameter 0.5mm has a resistivity of 0.016ohmm. The length of this wire that
will be necessarily to make a10 ohm coil is
a. 1226cm b. 1216ohm
c. 12266cm
d. 16622cm Ans: c
9. Electric current is
a. Both scalar as well as vector quantity
b. Scalar quantity
c. A vector quantity
d. A constant
Ans: b
10. An electric gyser uses the principle of
a. Magnetic effect of electric current
b. Electromagnetic induction
c. Chemical effect of electric current
d. Heating effect of electric current
Ans: d
11. A device which help to maintain a potential difference across a conductor is called
a. Ammeter
b. Voltmeter
c. Potentiometer
d. Electric Cell
Ans: d
12. A rheostat in an electric circuit is connected to
a. Stop the flow of current in the circuit
b. Apply a constant resistance in the circuit
c. Apply a variable resistance in the circuit
d. Start the flow of current in the circuit
Ans: c
13. kWh is the unit of
a. resistance
b. work done
c. electrical energy
d. power
Ans: c
14. A torch bulb is rated 2.5V and 750mA then the power will be
a. 2W
b. 1W
c. 1.87W
d. 3W
Ans: c
15. If a bulb is rated 100V, 50W then the resistance of the bulb will be
a. 200ohm
b. 100ohm
c. 50ohm
d. 10ohm
Ans: a
16. The metal used for making a fuse wire is
a. Copper
b. Steel
c. Tin
d. silver
Ans: c
17. Magnetic lines of force
a. Intersect within the magnet
b. Cannot intersect at all
c. Intersect at neutral points only
d. Intersect at N and S poles
Ans: b
18. The direction of magnetic field of earth is in
a. Northward direction
b. Eastward direction
c. Southward direction
d. West direction
Ans: a
19. Fuse and the switch are always connected to
a. earth wire
b. a neutral wire
c. a live wire
d. between any of the two wires
Ans: c
20. An AC generator
a. produces constant current
b. produces constant voltage
c. convert electrical energy into mechanical energy
d. produces alternating current
Ans: d
21. The working principle of a fuse is based on
a. Lenz’s law
b. Electromagnetic induction
c. Heating effect of electric current
d. Faraday’s law
Ans: c
22. The direction of the induced current is given by
a. Right hand thumb rule
b. Fleming left hand rule
c. Faraday’s law
d. Fleming’s right hand rule
Ans: d
23. A dynamo is a device to convert
a. potential energy into kinetic energy
b. kinetic energy into potential energy
c. chemical energy into electrical energy
d. mechanical energy into electrical energy
Ans: d
24. In an electric motor, the current is supplied in the coil through the
a. commutator rings
b. magnet
c. battery
d. carbon brushes
Ans: d
25. The characteristic of AC is
a. the magnitude does not vary with time
b. it has unidirectional current
c. its magnitude only changes with time
d. its magnitude and direction changes with time
Ans: d
26. The colour of a live wire is
a. red
b. black
c. brown
d. light blue
Ans: c
27. Consider that you are provided with a bar magnet and a coil. You can produce electric current
by
a. moving the magnet but not the coil
b. moving the coil but not the magnet
c. moving either the magnet or the coil
d. using another DC source
Ans: c
28. The closer the magnetic field lines
a. weaker is the field strength
b. stronger is the field strength
c. magnetic field is constant through out
d. none of these
Ans: b
29. One tesla is equal to
a. 104 gauss
b. 10-4gauss
c. 105 gauss
d. 106gauss
Ans: a
30. The power of a lens is -5D. Its focal length is
a. +5m
b. -5m
c. -5cm
d.-20cm
Ans: d
31. An object is placed between the optical centre and focus of a convex lens. The image formed
will be
a. virtual, erect and diminished
b. virtual, erect and magnified
c. real, inverted and diminished
d. real, inverted and magnified
Ans: b
32. The refractive index of a substance depends upon the
a. angle of incidence
b. angle of refraction
c. nature of the material and the wavelength of the light used
d. nature of the material only
Ans: c
33. The stars twinkle on a clear night sky is due to the
a. atmospheric refraction
b. dispersion of light
c. scattering of light
d. reflection of light
Ans: a
34. A ray of light directed towards the optical centre of a lens after refraction
a. passes through the focus
b. passes undeviated
c. become parallel to the principal axis
d. is reflected back
Ans: b
35. An object is placed at 10cm in front of the plane mirror .The image formed is
a. 10cm behind the mirror
b. 10cm infront of the mirror
c. 20cm behind the mirror
d. 20cm infront of the mirror
Ans: a
36. For a plane mirror the radius of curvature (R) is at
a. infinity
b. F
c. f/2
d. 0
Ans: a
37. The three primary colours of light are
a. yellow, red and blue
b. red, blue and green
c. red, white and blue
d. violet, green and red
Ans:b
38. The name of the hole, right in the middle of the iris is called
a. retina
b. blind spot
c. pupil
d. eye hole
Ans: c
39. The phenomenon of scattering of light by the colloidal particles is called
a. dispersion
b. reflection
c. refraction
d. Tyndall effect
Ans: d
40. The path of light through water can be visible on adding
a. salt b. Sugar c. Milk
d. Sand
Ans: c
41. For a hyper metropic eye, the near point is
a. 25cm b. Infinity c. Less than 25cm d. Greater than 25cm
Ans: d
42. Far point of a normal eye is
a. 25cm b. Infinity
c. Less than 25cm
d. Greater than 25cm
Ans: b
43. The radiation emitted by hot iron are
a. UV rays b. X rays
c. IR rays
d. γ rays
Ans: c
44. The tidal waves in ocean built up and recede
a. Once in a day b. Twice a day c. Thrice a day
d. Four times a day
Ans: b
45. The chemical added to LPG to detect leakage is
a. Carbon disulphide b. Mercaptan c. Ethane d. Methane
Ans: b
46. The contribution of nuclear power plants in the generation of electricity is equal to
a. equal to 30% b. Less than 3%
c. Equal to 3% d. Greater than 3%
Ans: b
47. The radiations responsible for skin cancer are
a. UV rays
b. IR rays
c. γ rays
d. X- rays
Ans: a
48. The energy due to difference in the temperature of water at the surface of the ocean and
deeper level is called
a. sea wave energy b. Tidal energy
c. Bio-energy
d. Ocean thermal energy
Ans: d
49. Non renewable source of energy is
a. ocean b. coal
c. Bio-fuels
d. Tides
Ans: b
50. The largest constituent of coal gas
a. ethylene
b. hydrogen
c. methane
d. carbon dioxide
Ans: c