64. Series traction motor operating on undulating dc supply has undulation ratio It equal to where 'max and Imia are respectively the maximum and minimum currents.
A. 'max 1mm I max
B.1max imm 1mM
C. 21 max
D.2l max

---

65. In a unsymmetrical three-phase line conductors are spaced at distances D12, D23 and D31. The equivalent distance D equals
A. D23 ? D31
B.D12 + D23 + D31
C.D12 + D23 + D3I
D. D12+D11+D22

---

66. Tidal energy mainly makes use of
A. kinetic energy of water
B. potential energy of water
C. both kinetic as well as potential energy of water
D. none of these

---

67. Maximum efficiency of an open cycle gas turbine is nearly
A.30%
B.40%
C.50%
D.60%

---

68. A 100 MW thermal power plant will consume nearly how many tonnes of coal in one hour?
A. 50 tonnes
B. 150 tonnes
C. 1500 tonnes
D. 15,000 tonnes

---

69. For economic operation, the generator with highet positive incremental transmission of loss will operate at
A. the lowest positive incremental cost of production.
B. the lowest negative incremental cost of production.
C. the highest positive incremental cost of production.
D. none of these

---

70. Insulation of the modern EHV lines is designed based on
A. lighting voltage
B. switching voltage
C. corona
D. RI

---