Basic electrical mcq 81-100

81. 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

82. Ohm’s law is not applicable to
(a) semi-conductors✔
(b) D.C. circuits
(c) small resistors
(d) high currents

83. Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional 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✔

84. 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

85. Temperature co-efficient of resistance is expressed in terms of
(a) ohms/°C
(b) mhos/ohm°C
(e) ohms/ohm°C✔
(d) mhos/°C

86. Which of the following materials has the least resistivity ?
(a) Zinc
(b) Lead
(c) Mercury
(d) Copper✔

87. 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

88. 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

89. Which of the following statement is correct ?
(a) A semi-conductor is a material whose conductivity is same as between that of a conductor and an insulator✔
(b) A semi-conductor is a material which has conductivity having average value of conductivity of metal and insulator
(c) A semi-conductor is one which con¬ducts only half of the applied voltage
(d) A semi-conductor is a material made of alternate layers of conducting material and insulator

90. A rheostat differs from potentiometer in the respect that it
(a) has lower wattage rating
(b) has higher wattage rating✔
(c) has large number of turns
(d) offers large number of tapping

91. The weight of an aluminium conductor as compared to a copper conductor of identical cross-section, for the same electrical resistance, is
(a) 50%✔
(b) 60%
(c) 100%
(d) 150%

92. An open resistor, when checked with an ohm-meter reads
(a) zero
(b) infinite✔
(c) high but within tolerance
(d) low but not zero

93. are the materials having electrical conductivity much less than most of the metals but much greater than that of typical insulators.
(a) Varistors
(b) Thermistor
(c) Semi-conductors✔
(d) Variable resistors

94. All good conductors have high
(a) conductance✔
(b) resistance
(c) reluctance
(d) thermal conductivity

95. Voltage dependent resistors are usually made from
(a) charcoal
(b) silicon carbide
(c) nichrome✔
(d) graphite

96. Voltage dependent resistors are used
(a) for inductive circuits
(6) to supress surges✔
(c) as heating elements
(d) as current stabilizers

97. The ratio of mass of proton to that of electron is nearly
(a) 1840✔
(b) 1840
(c) 30
(d) 4

98. The number of electrons in the outer most orbit of carbon atom is
(a) 3
(b) 4✔
(c) 6
(d) 7

99. With three resistances connected in parallel, if each dissipates 20 W the total power supplied by the voltage source equals
(a) 10 W
(b) 20 W
(c) 40 W
(d) 60 W✔

100. A thermistor has
(a) positive temperature coefficient
(b) negative temperature coefficient
(c) zero temperature coefficient
(d) variable temperature coefficient✔