FUNCTION -5 (ELECTRICAL)

151. 2 alternators are operating in parallel. If there is an increase in load and decrease in voltage, the AVR will
     1. cut out the field resistance
     2. cut in the field resistance
     3. cut in armature resistance
     4. cut out armature resistance

ANS.: A

152. A galvanometer is used to measure-
     1. small voltages
     2. small currents
     3. large currents
     4. large voltages

ANS.: B

153. In a 3 wire system the earth wire is colored
     1. red
     2. black
     3. white
     4. green

ANS.: D

154. A power factor meter in ECR shows-
     1. true power
     2. apparent power
     3. relationship between volts and amperes
     4. relationship between true power and apparent power

ANS.: D

155. Before synchronizing alternators, they must have
     1. load equalized
     2. same frequency
     3. same voltage
     4. same amperage

ANS.: B

156. The advantage of DC motors over AC motors is that, they have-
     1. higher speeds
     2. handle heavier loads
     3. have better speed control
     4. have a longer life

ANS.: C

157. Which of the following is not required for synchronizing alternators?
     1. same voltage
     2. same phase rotation
     3. same speed expressed as frequency
     4. same KW rating

ANS.: D

158. Temperatures in AC generators are indicated by-
     1. imbedded thermocouples
     2. deep well thermometers
     3. pyrometers
     4. standard thermometers

ANS.: A

159. If the resistance of a circuit is doubled and the applied voltage kept constant, the current will-
     1. increase 4 times
     2. be doubled
     3. cut into half
     4. no change

ANS.: C

160. If the polarity of a DC line is reversed the connecting motors will-
     1. stop
     2. increase in speed
     3. reverse
     4. rotate as before

ANS.: C

161. Which of the following parts of an AC motor corresponds to the armature of a DC motor-?
     1. field coils
     2. stator
     3. rotor
     4. armature

ANS.: B

162. Which of the following parts of an AC motor corresponds to the field of a DC motor?
     1. stator
     2. the field coils
     3. rotor
     4. armature

ANS.: C

163. The purpose of a commutator is to—
     1. keep a constant voltage
     2. rectify armature current
     3. convert magnetic lines of force into flux
     4. keep a constant amperage

ANS.: B

164. If a transformer was plugged into a DC circuit—
     1. the fuse would blow
     2. the primary would overload and the secondary would be dead
     3. the secondary would burn out
     4. any of above

ANS.: B

165. A megger is used to measure
     1. kilo ohms
     2. mega ohms
     3. milli ohms
     4. micro ohms

ANS.: B

166. A megger is a—
     1. hand cranked instrument for measuring current
     2. hand cranked AC generator
     3. hand cranked DC generator
     4. meter for measuring thickness of insulation

ANS.: C

167. When megger testing a new armature coil to ground-the readings should be at least-
     1. 1 meg
     2. 100 megs
     3. 1000 megs
     4. infinity

ANS.: A

168. An ammeter is connected to a circuit in
     1. series-parallel
     2. parallel
     3. series
     4. contact

ANS.: C

169. 60 cycles or Hertz means the cycle is repeated-
     1. 60 times a minute
     2. 60 times an hour
     3. 60 times a second
     4. none of above

ANS.: C

170. Doubling the diameter of a wire –
     1. increases the resistance 4 times
     2. reduces the resistance 4 times
     3. decreases the resistance 2 times
     4. increases the resistance 2 times

ANS.: B

171. Field excitation when required is always supplied from
     1. a source of DC
     2. an alternator
     3. a magnet
     4. a selenium rectifier.

ANS.: A

172. An oscilloscope can measure—
     1. peak voltage
     2. frequency
     3. phase angle
     4. all of the above

ANS.: D

173. For charging a lead acid battery, you allow a current to flow from an external EMF source through the battery
     1. in the same direction
     2. in the reverse direction
     3. current in same and reverse direction alternately.
     4. none of above

ANS.: B

174. A 2 pole alternator running at 3600 rpm can be paralleled with a 4 pole alternator running at—
     1. 3600 rpm
     2. 1800 rpm
     3. 900 rpm
     4. 7200 rpm

ANS.: B

175. What is the difference between an AC generator and a DC generator—
     1. AC generator has a commutator
     2. DC generator has slip rings
     3. AC generator has slip rings
     4. none of above

ANS.: C

176. What is the difference between a DC motor and a DC generator?
     1. DC generator does not have residual magnetism when put off
     2. there is no difference
     3. DC motor does not have commutator
     4. DC motors do not have interpoles

ANS.: B

177. If an AC generator on load slows down –
     1. current drops
     2. frequency drops
     3. voltage drops
     4. all of the above

ANS.: D

178. An electrical device for converting DC to AC is called
     1. transformer
     2. inverter
     3. rotary convertor
     4. synchronous converter

ANS.: B

179. If an AC generator was slowed down, the following would happen within limits
     1. voltage would increase
     2. amperes would increase
     3. frequency would increase
     4. all of the above

ANS.: B

180. A 3 phase system
     1. gives 3 distinct voltages out of step with each other
     2. has a peak voltage 3 times every 360 degrees
     3. is like comparing a single cylinder engine with a 3-cylinder engine
     4. all of the above

ANS.: D