The surge impedance

 Q201. The surge impedance of a line depends on:

A) Inductance and capacitance
B) Resistance and inductance
C) Conductance and capacitance
D) None
Ans: A

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Q202. The attenuation constant of a line is zero when:
A) Line is lossless
B) Line is open-circuited
C) Line is shorted
D) Line is distorted
Ans: A

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Q203. The phase constant (β) of a line determines:
A) Phase shift per unit length
B) Velocity of propagation
C) Wavelength
D) All of the above
Ans: D

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Q204. The characteristic impedance of a line is real when:
A) Line is lossless
B) Line is open-circuited
C) Line is distorted
D) None
Ans: A

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Q205. The surge impedance loading (SIL) for a 220 kV line (Zc = 400 Ω) is:
A) 120 MW
B) 121 MW
C) 125 MW
D) 130 MW
Ans: B

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Q206. When the line is open at receiving end, the reflected wave is:
A) In phase with incident wave
B) 180° out of phase
C) Zero
D) Random
Ans: A

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Q207. When the line is short-circuited at receiving end, the reflected wave is:
A) Inverted
B) Same phase
C) Zero
D) Doubled
Ans: A

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Q208. A quarter-wave line transforms:
A) Impedance to its inverse
B) Impedance to zero
C) Voltage to current
D) None
Ans: A

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Q209. The reflection coefficient at the load end is given by:
A) $(Z_L - Z_c)/(Z_L + Z_c)$
B) $(Z_c - Z_L)/(Z_c + Z_L)$
C) $Z_L Z_c$
D) None
Ans: A

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Q210. The input impedance of a line is equal to the load impedance when:
A) Line length = nλ/2
B) Line length = λ/4
C) Line length = λ
D) None
Ans: A

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Q211. The wavelength of a 50 Hz line with velocity $3 × 10^8$ m/s is:
A) 6000 km
B) 5000 km
C) 4000 km
D) 3000 km
Ans: A

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Q212. For distortionless transmission, the condition is:
A) $R/L = G/C$
B) $R/C = G/L$
C) $R = G$
D) $L = C$
Ans: A

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Q213. The velocity of propagation in a cable is less than that in air due to:
A) Dielectric medium
B) Capacitance
C) Inductance
D) Both A and B
Ans: A

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Q214. The Ferranti effect is more pronounced at:
A) Light load and long lines
B) Heavy load and short lines
C) Light load and short lines
D) None
Ans: A

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Q215. The sending-end voltage in Ferranti effect is:
A) Less than receiving-end
B) Equal
C) Greater
D) None
Ans: A

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Q216. A transmission line can be assumed lossless if:
A) R and G are negligible
B) R and G are large
C) R = G
D) None
Ans: A

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Q217. The corona effect is more in:
A) High voltage, small spacing
B) High voltage, large spacing
C) Low voltage, large spacing
D) None
Ans: A

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Q218. The corona loss increases with:
A) Increase in voltage
B) Decrease in conductor diameter
C) Decrease in spacing
D) All
Ans: D

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Q219. The electric field around a conductor is maximum at:
A) Conductor surface
B) Midpoint between conductors
C) Ground
D) Infinity
Ans: A

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Q220. The corona inception voltage increases with:
A) Increase in conductor diameter
B) Increase in air density
C) Increase in spacing
D) All
Ans: D

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Q221. Corona results in:
A) Power loss
B) Radio interference
C) Audible noise
D) All
Ans: D

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Q222. The presence of moisture in air:
A) Lowers corona inception voltage
B) Increases it
C) No effect
D) None
Ans: A

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Q223. Bundled conductors are used to:
A) Reduce corona
B) Increase line capacitance
C) Reduce reactance
D) All
Ans: D

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Q224. The spacing between sub-conductors in a bundle is typically:
A) 0.3–0.6 m
B) 1–2 m
C) 5 m
D) None
Ans: A

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Q225. The traveling wave current at a short-circuited end is:
A) Double
B) Zero voltage
C) Same as incident
D) None
Ans: B

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Q226. The surge impedance of a coaxial cable is:
A) 40–60 Ω
B) 100–200 Ω
C) 300–600 Ω
D) 10–20 Ω
Ans: A

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Q227. The term “standing wave” occurs due to:
A) Interference of incident and reflected waves
B) Single traveling wave
C) Voltage drop
D) None
Ans: A

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Q228. The standing wave ratio (SWR) is 1 when:
A) Line is matched
B) Line is shorted
C) Line is open
D) Line is mismatched
Ans: A

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Q229. For an open line, reflection coefficient =
A) +1
B) -1
C) 0
D) None
Ans: A

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Q230. For a shorted line, reflection coefficient =
A) -1
B) +1
C) 0
D) None
Ans: A

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Q231. The input impedance of a quarter-wave open line is:
A) Zero
B) Infinite
C) Equal to Zc
D) None
Ans: A

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Q232. The input impedance of a quarter-wave shorted line is:
A) Infinite
B) Zero
C) Equal to Zc
D) None
Ans: A

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Q233. The velocity of propagation is given by:
A) $v = 1/\sqrt{LC}$
B) $v = \sqrt{LC}$
C) $v = 1/LC$
D) None
Ans: A

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Q234. The propagation constant for a lossless line is:
A) $j\beta$
B) $\alpha + j\beta$
C) $\alpha$
D) None
Ans: A

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Q235. A line having R = G = 0 is:
A) Lossless
B) Distortionless
C) Ideal
D) Both A & C
Ans: D

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Q236. The reflection coefficient magnitude lies between:
A) 0 and 1
B) 0 and ∞
C) -1 and 1
D) None
Ans: A

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Q237. For perfect matching:
A) ZL = Zc
B) Γ = 0
C) SWR = 1
D) All
Ans: D

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Q238. The voltage standing wave ratio is given by:
A) $\frac{1 + |\Gamma|}{1 - |\Gamma|}$
B) $\frac{1 - |\Gamma|}{1 + |\Gamma|}$
C) $1 - |\Gamma|$
D) None
Ans: A

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Q239. The phase velocity of the wave depends on:
A) Medium
B) Frequency
C) Both
D) None
Ans: A

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Q240. The surge impedance of an underground cable is typically:
A) 40–60 Ω
B) 100–200 Ω
C) 300 Ω
D) 500 Ω
Ans: A

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Q241. The inductance per phase of a line increases with:
A) Increase in spacing
B) Decrease in spacing
C) Increase in conductor size
D) None
Ans: A

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Q242. Capacitance per phase increases with:
A) Decrease in spacing
B) Increase in conductor size
C) Both
D) None
Ans: C

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Q243. Corona loss is proportional to:
A) f + 25
B) f + 50
C) f
D) 1/f
Ans: A

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Q244. The units of surge impedance loading are:
A) MW
B) MVA
C) kV
D) Ω
Ans: A

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Q245. Surge impedance loading is given by:
A) $V^2 / Z_c$
B) $V/Z_c^2$
C) $V^2 Z_c$
D) None
Ans: A

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Q246. If load = SIL, then:
A) Voltage and current in phase
B) Voltage drop = 0
C) Line at unity PF
D) All
Ans: D

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Q247. The reflection coefficient for ZL = 0 is:
A) -1
B) +1
C) 0
D) ∞
Ans: A

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Q248. The reflection coefficient for ZL = ∞ is:
A) +1
B) -1
C) 0
D) ∞
Ans: A

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Q249. In power transmission, “steady-state stability limit” refers to:
A) Maximum power transferable without losing synchronism
B) Maximum voltage
C) Maximum current
D) None
Ans: A

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Q250. The maximum power transfer for a line is $V_s V_r / X \sin δ_{max}$. For max power:
A) δ = 90°
B) δ = 0°
C) δ = 45°
D) δ = 60°
Ans: A