BASIC ELECTRICAL PART 3

BASIC ELECTRICAL PART 3

121. Where do the ‘correctly terminated asymmetrical networks’ show
termination at both the ports of network?
a. In image impedances
b. In iterative impedances
c. In characteristic impedances
d. All of the above
ANSWER: A
122. Which unit is used for the measurement of an insertion loss?
a. Neper
b. Weber
c. Ohm
d. Watt
ANSWER: A
123. How is an insertion loss represented in terms of power ratio?
a. α = 10 log10 | P1 / P2 | decibel
b. α = 10 log10 | P2 / P1 | decibel
c. α = 20 log10 | P1 / P2 | decibel
d. α = 20 log10 | P2 / P1 | decibel
ANSWER: A
124. When converting from a current source to a voltage source, the
________ will remain the same.
A) current
B) voltage
C) no load current
D) resistance
Ans D
125 .An ideal current source has
a) Infinite source resistance
b) Zero internal resistance
c)Zero voltage on no load
d) Zero ripple
Ans-A
126. An ideal voltage source should have
a) Zero source resistance b) Infinite source
resistance
c)Terminal voltage is proportional to current d) Open-circuit voltage
nearly
equal to voltage of the
load current
Ans-A
127 .Identify the passive element among the following
a. Voltage source b. current source
c. inductor d.transistor
Ans-C
128.Which of the following is not the same as watt?
(A)joule/sec (B) amperes/volt
C) amperes x volt (D) ( amperes )2 x ohm.
Ans-B
129 . For a coil having a magnetic circuit of constant reluctance, the flux is
___________ to the current.
a) Directly proportional
b) Inversely proportional
c) Not related
d) Very large compared to
Answer: a
130. If either the inductance or the rate of change of current is doubled,
the induced e.m.f?
a) Remains constant
b) Becomes zero
c) Doubles
d) Becomes half
Answer: c
131. Which of the following is secondary cell?
(A) Dry cell
(B) Leclanche cell
(C) Voltaic cell
(D) Lead acid cell
ANS-D
132. Specific gravity of a fully charged lead acid cell is approximately:
(A) 1.18
(B) 1.21
(C) 1.17
(D) 1.16
ANS-B
133. What is The Basic Three Electrical Quantities.
a.Resistance, Capacitance, Inductance
b.Power, Voltage, Conductance
c.Voltage, Current, Resistance(Impedance)
c.Current , Reluctance, InductanCE
Answer: C
134. If the resistance in parallel with a parallel resonant circuit is
reduced, the bandwidth
A. disappears
B. becomes sharper
C. increases
D. decreases
Answer: D
135. If the value of C in a series RLC circuit is decreased, the resonant
frequency
A.is not affected
B.increases
C.is reduced to zero
D.decreases
Answer: B
136. A certain series RLC circuit with a 200 Hz, 15 V ac source has the
following values: R = 12 , C = 80 F, and L = 10 mH. The total
impedance, expressed in polar form, is
A.12.28 12.34°
B.12.57 12.34°
C.9.95 12.34°
D.12.62 12.34°
Answer: A
137. A 6 V battery is connected to a 300 load. Under these conditions, it
is rated at 40 Ah. How long can it supply current to the load?
A.1 h
B.200 h
C.2,000 h
D.10 h
Answer: C
138. For a given wirewound core, an increase in current through the coil
A. reverses the flux lines
B.decreases the flux density
C.increases the flux density
D.causes no change in flux density
Answer: C
139. When the current through the coil of an electromagnet reverses, the
A.direction of the magnetic field reverses
B.direction of the magnetic field remains unchanged
C.magnetic field expands
D.magnetic field collapses
Answer: A
140. If the steel disk in a crankshaft position sensor has stopped with the
tab in the magnet's air gap, the induced voltage
A. increases
B. decreases
C. is zero
D. will remain constant
Answer: C
141.The unit for permeability is
A. Wb/At × m
B. At/m
C. At/Wb
D. Wb
Answer: A
142. The induced voltage across a stationary conductor in a stationary
magnetic field is
A.Zero
B.reversed in polarity
C.increased
D.decreased
Answer: A
143. Which of the following capacitors is polarized?
A.Mica
B.ceramic
C.plastic-film
D.electrolytic
Answer: D
144. A 220 resistor is in series with a 2.2 F capacitor. The time
constant is
A.48 s
B.480 s
C.2.42 s
D.24 s
Answer: B
145. Of the following capacitors, which one has the highest dielectric
constant?
A.Air
B.Mica
C.Glass
D.Paper
Answer: C
146. When the plate area of a capacitor increases,
A.the capacitance increases
B.the capacitance decreases
C.the capacitance is unaffected
D.the voltage it can withstand increases.
Answer: A
147.When the voltage across a capacitor is tripled, the stored charge
A.Triples
B.is cut to one-third
C.stays the same
D.doubles
Answer: A
148.The resistance of insulators __________
a) Increases with increase in temperature
b) Decreases with increase in temperature
c) Remains the same with increase in temperature
d) Becomes zero with increase in temperature
Answer: b
149. What is the unit of temperature coefficient?
a) ohm/centigrade
b) ohm-centigrade
c) centigrade-1
d) centigrade
Answer: c
150. If the temperature is increased in semi-conductors such that the
resistance incessantly falls, it is termed as_______
a) Avalanche breakdown
b) Zener breakdown
c) Thermal runway
d) Avalanche runway
Answer c
151. The property of coil by which a counter e.m.f. is induced in it when
the current
through the coil changes is known as
(a) self-inductance
(b) mutual inductance
(c) series aiding inductance
(d) capacitance
Ans: a
152. As per Faraday’s laws of electromagnetic induction, an e.m.f. is
induced in a
conductor whenever it
(a) lies perpendicular to the magnetic flux
(b) lies in a magnetic field
(e) cuts magnetic flux
(d) moves parallel to the direction of the magnetic field
Ans: c
153. Which of the following circuit element stores energy in the
electromagneticfield ?
(a) Inductance
(b) Condenser
(c) Variable resistor
(d) Resistance
Ans: a
154. The inductance of a coil will increase under all the following
conditions except
(a) when more length for the same number of turns is provided
(6) when the number of turns of the coil increase
(c) when more area for each turn is provided
(d) when permeability of the core increases
Ans: a
155. Higher the self-inductance of a coil,
(a) lesser its weber-turns
(b) lower the e.m.f. induced
(c) greater the flux produced by it
(d) longer the delay in establishing steady current through it
Ans: d
156. In an iron cored coil the iron core is removed so that the coil becomes
an air
cored coil. The inductance of the coil will
(a) increase
(b) decrease
(c) remain the same
(d) initially increase and then decrease
Ans: b
157. An open coil has
(a) zero resistance and inductance
(b) infinite resistance and zero inductance
(c) infinite resistance and normal inductance
(d) zero resistance and high inductance
Ans: b
158. Both the number of turns and the core length of an inductive coil are
doubled.
Its self-inductance will be
(a) unaffected
(b) doubled
(c) halved
(d) quadrupled
Ans: b
159. If current in a conductor increases then according to Lenz’s law selfinduced
voltage will
(a) aid the increasing current
(b) tend to decrease the amount of cur-rent
(c) produce current opposite to the in-creasing current
(d) aid the applied voltage
Ans: c
160. The direction of induced e.m.f. can be found by
(a) Laplace’s law
(b) Lenz’s law
(c) Fleming’s right hand rule
(d) Kirchhoff s voltage law
Ans: b
161. Air-core coils are practically free from
(a) hysteresis losses
(b) eddy current losses
(c) both (a) and (b)
(d) none of the above
Ans: c
162. The magnitude of the induced e.m.f. in a conductor depends on the
(a) flux density of the magnetic field
(b) amount of flux cut
(c) amount of flux linkages
(d) rate of change of flux-linkages
Ans: d
163. Mutually inductance between two magnetically-coupled coils depends
on
(a) permeability of the core
(b) the number of their turns
(c) cross-sectional area of their common core
(d) all of the above
Ans: d
164. A laminated iron core has reduced eddy-current losses because
(a) more wire can be used with less D.C. resistance in coil
(b) the laminations are insulated from each other
(c) the magnetic flux is concentrated in the air gap of the core
(d) the laminations are stacked vertfcally
Ans: b
165. The law that the induced e.m.f. and current always oppose the cause
producing them is due to
(a) Faraday
(b) Lenz
(c) Newton
(d) Coulomb
Ans: b
166. Which of the following is not a unit of inductance ?
(a) Henry
(b) Coulomb/volt ampere
(c) Volt second per ampere
(d) All of the above
Ans: b
167. In case of an inductance, current is proportional to
(a) voltage across the inductance
(b) magnetic field
(c) both (a) and (b)
(d) neither (a) nor (b)
Ans: b
168. Which of the following circuit elements will oppose the change in
circuit current ?
(a) Capacitance
(b) Inductance
(c) Resistance
(d) All of the above
Ans: b
169. For a purely inductive circuit which of the following is true ?
(a) Apparent power is zero
(b) Relative power is.zero
(c) Actual power of the circuit is zero
(d) Any capacitance even if present in the circuit will not be charged
Ans: c
170. Which of the following is unit of inductance ?
(a) Ohm
(b) Henry
(c) Ampere turns
(d) Webers/metre
Ans: b
171. An e.m.f. of 16 volts is induced in a coil of inductance 4H. The rate of
change of current must be
(a) 64 A/s
(b) 32 A/s
(c) 16 A/s
(d) 4 A/s
Ans: d
172. The core of a coil has a length of 200 mm. The inductance of coil is 6mH. If
the core length is doubled, all other quantities, remaining the same, the
inductance will be
(a) 3 mH
(b) 12 mH
(c) 24mH
(d)48mH
Ans: a
173. The self inductances of two coils are 8 mH and 18 mH. If the coefficients of
coupling is 0.5, the mutual inductance of the coils is
(a) 4 mH
(b) 5 mH
(c) 6 mH
(d) 12 mH
Ans: c
174. Two coils have inductances of 8 mH and 18 mH and a co-efficient of coupling
of 0.5. If the two coils are connected in series aiding, the total inductance
will be
(a) 32 mH
(b) 38 mH
(c) 40 mH
(d) 48 mH
Ans: b
175. A 200 turn coil has an inductance of 12 mH. If the number of turns is
increased to 400 turns, all other quantities (area, length etc.) remainingthe same,
the inductance will be
(a) 6 mH
(b) 14 mH
(c) 24 mH
(d) 48 mH
Ans: d


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