FUNCTION -5 (ELECTRICAL)

121. What is residual magnetism?
     1. Magnetism in a solenoid coil
     2. Magnetism in a natural magnet
     3. Magnetism remaining after magnetic field is removed
     4. None of the above

ANS.: C

122. Which of the following is / are true about earthing of high voltage installations?
     1. High voltage installations should not be earthed at the star point of the generator
     2. Neutral earthing resonance can be used for earthing high voltage installations
     3. The value of the NER is usually selected to limit current to the full load current value
     4. NERs can be substituted with earthing arrangements at circuit breakers in high voltage installations to achieve the same effect

ANS.: B,C

123. The circuit efficiency of a class A amplifier can be increased by using
     1. Low DC power input
     2. Direct coupled load
     3. Low rating transistor
     4. Transformer coupled load

ANS.: D

124. The negative plate of a nickel cadmium battery after discharge consists of __________
     1. Nickel hydroxide
     2. Cadmium hydroxide
     3. Potassium hydroxide
     4. Cadmium

ANS.: B

125. Which of the following is / are true about regulation concerning shipboard storage batteries?
     1. Construction should always be so as to prevent emission of spray
     2. If voltage is above 220 V, insulation stands must be used
     3. The deck below the cells should be protected with acid resisting or alkaline resisting material
     4. Battery banks above 2KW should be kept in the battery room

ANS.: A,C,D

126. Which of the following are TRUE with regards to Bi-metal strips?
     1. Bi-metal strips are generally used for temperature sensing
     2. Bi-metal strips are generally used for power control
     3. Bi-metal strips are generally used for voltage regulations
     4. Bi-metal strips are generally used as thermal elements in an over current protection relay

ANS.:  A,C,D

127. Which of the following system is normally used in high voltage (3.3 KV and above) generation and primary distribution?
     1. AC single phase two wire insulated
     2. AC three phase three wire insulated
     3. DC two wire insulated
     4. AC three phase three wire, neutral earthed

ANS.: D

128. Which of the following protection devices are not provided for motors used in operation of electro hydraulic steering gears?
     1. Fuses
     2. Overload alarm
     3. Overload trip
     4. Power failure alarm

ANS.: C

129. Which of the listed devices may be installed on a large turbo electric alternating current propulsion generator?

1. Temperature detector coils inserted in the stator slots for measuring stator temperature
2. Electric space heaters to prevent condensation of moisture
3. CO2 fire extinguishing system

1. I, II and III
2. I and II
3. II and III
4. III only

ANS.: A

130. The depletion region in semiconductor diode is due to
     1. Reverse biasing
     2. Forward biasing
     3. Crystal doping
     4. Migration of mobile charge carriers

ANS.: D

131. Which of the following statement is false?
     1. An insulated distribution system needs two earth faults on two different lines to cause a earth fault current
     2. An earthed distribution system requires only one earth fault on one line to cause a earth fault current
     3. An insulated system is more effective in maintaining continuity of supply to electrical equipment
     4. None of the above

ANS.: D

132. Current flow in a semiconductor depends on the phenomenon of
     1. Drift
     2. Diffusion
     3. Recombination
     4. All of the above

ANS.: D

133. The purpose of a cage rotor winding placed on the rotor of a synchronous motor is to
     1. Provide excitation to the DC field
     2. Start the machine as induction motor
     3. Contribute extra torque at synchronous speed
     4. Prevent the machine from falling out of step

ANS.: B

134. Which of the following is / are true of starters used for electric motors?
     1. Capacitor start can be used only with slip ring motors
     2. Rheostat starters are based on semiconductor
     3. Frequency converters can also be used as starters
     4. The effect of an auto transformer start is similar to that of reactor start

ANS.: C,D

135. A LED emits visible light when its ___________
     1. PN junction is reverse biased
     2. Depletion region widens
     3. Holes and electrons recombine
     4. PN junction becomes hot

ANS.: C

136. Which of the following can cause ―Grounds‖ occurring in electrical machinery as a result of insulation failure?
     1. Deterioration through extended use
     2. Excessive heat
     3. Operating in extremely cold conditions
     4. Extended periods of vibration

1. I and II only
2. II and IV only
3. I, II and III
4. I, II, III and IV

ANS.: D

137. For faithful amplification, a transistor must
     1. Input forward biased
     2. Output reverse biased
     3. Work in operating point
     4. All of the above

ANS.: D

138. In a system of standby synchronizing lamps fitted in conjunction with a synchronoscope to synchronize an AC Generator

• Lamp #1 is connected between S line of live bus bars and S line of incoming alternator,
• Lamp #2 is connected between R line of live bus bars and T line of incoming alternator,
• Lamp #3 is connected between T line of live bus bars and R line of incoming alternator.

Which of the following is the right trigger for choosing the circuit breaker?

1. When lamp #1 is dark and lamp #2 and #3 are equally bright
2. When lamp #1 is dark, lamp #2 is low in brightness and lamp #3 is very bright
3. When all three lamps are equally bright
4. When all three lamps are dark

ANS.: A

139. Proper storage battery maintenance would include
     1. Maintaining a high charging current at all times
     2. Maintaining connections tight
     3. Checking weight of batteries from time to time
     4. All of the above

ANS.: B

140. The circuit efficiency of a class A amplifier can be increased by using
     1. Low dc power input
     2. Direct coupled load
     3. Low rating transistor
     4. Transformer coupled load

ANS.: D

141. Maximum reverse voltage that can be applied to the PN Junction without damage is termed as: –
     1. Reverse bias voltage
     2. Peak inverse voltage
     3. Breakdown voltage
     4. Zener voltage

ANS.: B

142. The width of the depletion layer of a PN Junction
     1. Decreases with light doping
     2. Increases with heavy doping
     3. Is independent of supply voltage
     4. Is increased under reverse bias

ANS.: D

143. Power transformers are rated in
     1. kilowatts
     2. ampere-turns
     3. kilowatt-volts
     4. kilovolt-amperes

ANS.: D

144. The purpose of a main switchboard circuit breakers reverse-power trip is to
     1. prevent main circuit overload
     2. protect the circuit breaker blowout coil
     3. prevent alternator motorization
     4. prevent low voltage trip out

ANS.: C

145. The charge of an alkaline battery is determined with a—
     1. hydrometer
     2. ammeter
     3. voltmeter
     4. hygrometer

ANS.: C

146. If the pointer fails to come back to zero when the megger is not in use it means—
     1. the megger is out of calibration
     2. this is normal
     3. the hairsprings are burnt out
     4. the pointer is stuck

ANS.: B

147. The power factor of an induction motor operating at full load is-
     1. leading
     2. lagging
     3. unity
     4. no change

ANS.: B

148. In a 3 phase delta connection, the line current will be the product of phase current and
     1. 501
     2. 216
     3. 414
     4. 732

ANS.: D

149. The principal difference between a 3 phase squirrel cage induction motor and a single phase induction motor is-
     1. one is a split phase motor using a capacitor, while the other uses an inductor
     2. one has a revolving field which drags the rotor slightly behind it, while the other runs in step.
     3. there is no difference
     4. one needs DC excitation, the other need no excitation

ANS.: A

150. Which of the following devices are used for protection of AC propulsion motors and generators?
     1. jamming relays
     2. low voltage release
     3. timing relays
     4. phase balance relays

ANS.: D