76. When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will
(a) decrease
(b) increase
(c) remain constant
(d) none of the above
Ans: b
77. A field of force can exist only between
(a) two molecules
(b) two ions
(c) two atoms
(d) two metal particles
Ans: b
78. A substance whose molecules consist of dissimilar atoms is called
(a) semiconductor
(b) superconducto
(c) compound
(d) insulator
Ans: c
79. International ohm is defined in terms of the resistance of
(a) a column of mercury
(b) a cube of carbon
(c) a cube of copper
(d) the unit length of wire
Ans: a
80. Three identical resistors are first connected in parallel and then in series.The resultant resistance of the first combination to the second will be
(a) 9 times
(b) 1/9 times
(c) 1/3 times
(d) 3 times
Ans: b
91. Which method can be used for absolute measurement of resistances ?
(a) Lorentz method
(b) Releigh method
(c) Ohm’s law method
(d) Wheatstone bridge method
Ans: d
92. Three 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners ?
(a) 3/2 Q
(b 6 Q
(c) 4 Q
(d) 8/3 Q
Ans: c
93. Ohm’s law is not applicable to
(a) semiconductors
(b) D.C. circuits
(c) small resistors
(d) high currents
Ans: a
94. Two copper conductors have equal length. The crosssectional area of one conductor is four times that of the other. If the conductor having smaller crosssectional area has a resistance of 40 ohms the resistance of other conductor will be
(a) 160 ohms
(b) 80 ohms
(c) 20 ohms
(d) 10 ohms
Ans: d
95. A nichrome wire used as a heater coil has the resistance of 2 £2/m. For a heater of 1 kW at 200 V, the length of wire required will be
(a) 80 m
(b) 60 m
(c) 40 m
(d) 20 m
Ans: a
96. Temperature coefficient
of resistance is expressed in terms of
(a) ohms/°C
(b) mhos/ohm°C
(e) ohms/ohm°C
(d) mhos/°C
Ans: c
97. Which of the following materials has the least resistivity ?
(a) Zinc
(b) Lead
(c) Mercury
(d) Copper
Ans:
98. When current flows through heater coil it glows but supply wiring does not glow because
(a) current through supply line flows at slower speed
(b) supply wiring is covered with insulation layer
(c) resistance of heater coil is more than the supply wires
(d) supply wires are made of superior material
Ans: c
99. The condition for the validity under Ohm’s law is that
(a) resistance must be uniform
(b) current should be proportional to the size of the resistance
(c) resistance must be wire wound type
(d) temperature at positive end should be more than the temperature at negative end
Ans: a
100. Which of the following statement is correct ?
(a) A semiconductor is a material whose conductivity is same as between that of a conductor and an insulator
(b) A semiconductor is a material which has conductivity having average value of conductivity of metal and insulator
(c) A semiconductor is one which con¬ducts only half of the applied voltage
(d) A semiconductor is a material made of alternate layers of conducting material and insulator
Ans: a
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TNPSC Master
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