75. Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes
(a) 1/9 times
(b) 3 times
(e) 9 times
(d) unchanged
Ans: c
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) semi-conductor
(b) super-conducto
(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