1. 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
Ans: d
2. A thermistor has
(a) positive temperature
coefficient
(b) negative temperature
coefficient
(c) zero temperature
coefficient
(d) variable temperature
coefficient
3. If/, R and t are the
current, resistance and time respectively, then according to Joule’s law heat
produced will be proportional to
(a) I2Rt
(b) I2Rf
(c) I2R2t
(d) I2R2t*
Ans: a
4. A substance whose molecules consist of dissimilar atoms is
called
(a) semi-conductor
(b) super-conductor
(c) compound
(d) insulator
Ans: c
5. 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
6. 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
7. Nichrome wire is an alloy of
(a) lead and zinc
(b) chromium and vanadium
(c) nickel and chromium
(d) copper and silver
Ans: c
8. Switching of a lamp in house produces noise in the radio. This
is because switching operation produces
(a) arcs across separating
contacts
(b) mechanical noise of high
intensity
(c) both mechanical noise and
arc between contacts
(d) none of the above
Ans: a
9. Sparking occurs when a load
is switched off because the circuit has high
(a) resistance
(b) inductance
(c) capacitance
(d) impedance
Ans: b
10. A field of force can exist only between
(a) two molecules
(b) two ions
(c) two atoms
(d) two metal particles
Ans: b
11. 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
12. 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
13. 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
14. 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
15. Ohm’s law is not applicable
to
(a) semi-conductors
(b) D.C. circuits
(c) small resistors
(d) high currents
Ans: a
16. Which of the following
materials has the least resistivity ?
(a) Zinc
(b) Lead
(c) Mercury
(d) Copper
Ans: d
17. 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
18. 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
19. 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
Ans: a
20. 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
Ans: b
