Description : Explain what happens if a DC motor is fed with AC supply
Last Answer : Motor will run at low speed, sparking at brushes, heat due to eddy current will finally burn the motor.
Description : The output from a full wave rectifier is (a) A pulsating uni-directional current (b) A DC voltage (c) Zero (d) An AC voltage
Last Answer : a) A pulsating uni-directional current
Description : In a half wave rectifier the rms value of AC component of the waves (a) Zero (b) Equal to DC value (c) More than DC value (d) Less than DC value
Last Answer : b) Equal to DC value
Description : The process of conversion of AC into DC is called (a) Amplification (b) rectification (c) purification (d)magnification
Last Answer : (b) rectification
Description : The only difference between construction of DC generator and Ac generator is that of: a. carbon brush b. Bar magnet c. electromagnet d. Horseshoe magnet
Last Answer : b. Bar magnet
Description : Which of the following converts electric energy into mechanical energy: a. Transformer b. DC generator c. Motor d. AC generator
Last Answer : d. AC generato
Description : Is the ship's alternator Star wound or Delta wound?
Last Answer : Refer Dennis T Hall
Description : Does current flow through hull during welding?
Last Answer : Ask E/O. Yes I think
Description : Why is it different from that for welding?
Last Answer : It is higher as the ignition requires break down of air gap for park to occur. The air breaks down at this high voltage of 10kV. Therefore, it is higher than normal welding voltage.
Description : How does current flow during welding?
Last Answer : The current flows through the electrode and to the clamp. That's how it flows in MIG, stick, flux cored. On Tig, the electricity flows through the electrode also except that now that's the only function of it, the rod is held in your hand and electrode in the other.
Description : When MMA welding what will be the effect on the weld f the power source was changed from AC to DC-ve? a) None b) Higher deposition rate c) It would slightly increase the depth of penetration d) The arc would become unstable
Last Answer : b) Higher deposition rate
Description : Compare DC and AC welding on any four points.
Last Answer : Points DC Welding AC Welding Supply equipment used DC differential Compound Generator, or Rectifier Welding Transformer Heating Effect Uniform Not Uniform Temperature Obtain ... High, 85% Application Carbon Arc Welding Resistance Welding , Metal Arc Welding
Description : Why is DC not much in use now?
Last Answer : AC generators are a better technology and voltage transformation (by transformers) is easy is possible in AC and not DC.
Description : What are the basic parts of a DC motor?*
Last Answer : Rotor and stator, field poles, commutator, brushes, fan impeller, bearing & housing, end covers and name plate.
Description : How is the speed of a DC motor varied?
Last Answer : To vary the speed of a DC motor we need a constant voltage power supply with a series POT resistor of higher watt rating. A Pulse Width Modulator (PWM) can be used.
Description : Is there phase in DC?
Last Answer : No
Description : Which component is mainly used in a DC generator: a.slip ring b. commutator c. magnet d. coil
Last Answer : b. commutator
Description : Direct Current (DC) Next Topic : Alternating current (AC)
Last Answer : Direct Current (DC) is the unidirectional electric current. Uni meaning is one. And the flow of charge in same direction. We know that conventional current flow from positive terminal of battery to ... The magnitude of DC may constant or vary but direction do not change with respect to time.
Last Answer : Primary Idea : - First Home Type Understand AC To buy Will be That In the room AC Put it on In that If The window Stays However Likes According to Good Brand See ' window AC ' Bought To take Can. Of ... go 45 From 60 Thousands Money In The same Price In ' Gree ' Of the brand Window AC Found Will go
Description : Where is a rotor wound AC motor used?
Last Answer : For starting heavy torques, mostly used on portable machines and small winches.
Description : How can the direction of rotation of an AC motor be reversed?*
Last Answer : By interchanging any two supply lines.
Description : What are the parts of a brushless AC generator?
Last Answer : Yoke, armature, stator, rotor, primary exciter, main exciter, rotary diode rectifier assembly, impeller, bearing & housing, end cover, terminal block, AVR.
Description : What is meant by phase in AC?
Last Answer : Two or more AC voltages or currents that are out of step with each other. Their peaks and zero points do not match up at the same points in time. This is meant by phase.
Description : Capacity of battery fuse in AC Coaches a. 315 A & 400 (HRC ) c. 16 A (HRC ) b. 63 A (HRC ) d. 5 A (HRC )
Last Answer : a. 315 A & 400 (HRC )
Description : In the plane of AC generator coil is parallel to the field, then emf induced in coil is: a. maximum b. minimum c. zero d. intermediate
Last Answer : b. minimum
Description : Which one is not present in AC generator: a. Armature b. magnet c. slip ring d. commutator
Last Answer : c. slip ring
Description : The most common source of AC voltage is: a. motor b. generator c. cell d. transformer
Last Answer : c. cell
Description : The principle of AC generator is: a. Mutual induction b. self induction c. electromagnetic induction d. Induction
Last Answer : b. self induction
Description : Turn ratio of a transformer is 5. If 220 V AC is applied to its primary coil, voltage in the secondary coil will be: a. 44V b. 4.4 V c. 220V d. 1100V
Last Answer : c. 220V
Description : Alternating current (AC)
Last Answer : AC stands for Alternating Current meaning voltage or current that changes polarity or direction respectively over time. An Alternating Current (AC) is an electric current whose magnitude ... energy are known as alternators and are simpler construction than DC electromechanical generators.
Description : When using a megohmmeter to determine which shunt field coil is grounded in a DC machine, you must ____________. A. insulate the field frame from the ship's hull B. disconnect each shunt ... C. use a motor driven high capacity megohmmeter D. remove all main line lead connections before testing
Last Answer : Answer: B
Description : An electrical device which employs a stationary armature and a rotating electromagnetic field is used aboard ship as a ____________. A. magnetic amplifier B. ship's service alternator C. three-wire DC generator D. saturable core reactor
Description : On some diesel-electric ships, the DC propulsion motor will only attain half speed when the generator fields are fully excited. Speeds above this are obtained by _____________. A. rotating brush ... B. raising the generator engine speed C. lowering the generator engine speed D. decreasing excitation
Description : Transformers are used onboard ships with AC generators to _____________. A. change frequency B. increase power output to modulating frequency controllers C. decrease power output to modulating frequency ... D. permit higher voltage for electric motor operation and low voltage for lighting circuits
Last Answer : Answer: D
Description : Ships’ generators produce 450-volt, three-phase, ac power; however, most equipment uses 117-volt, single-phase power What transformers and connections are used to convert 450- volt, threephase power to 117-volt, single-phase power?
Last Answer : A method of generating oscillations, a method of turning the oscillations on and off (keying), and an antenna to radiate the energy.
Description : The required DC voltage for arc welding is- (1) 6 to 9 V (2) 50 to 60 V (3) 200 to 250 V (4) 90 to 100 V
Last Answer : (3) 200 to 250 V
Description : A butt weld has been made by MMA in a 50mm thick impact tested steel plate. The welding electrode used was a basic type, 5mm diameter. The measured welding parameters for one of the runs was 250 amps, 24 volts, using DC ... given to calculate the arc energy b) 1.9 kJ/mm c) 1.87 kJ/mm d) 2.0 kJ/mm
Last Answer : d) 2.0 kJ/mm
Description : Which of the following generators is used for DC arc welding application ? (A) Series generator (B) Shunt generator (C) Differential compound generator (D) Over -compound generator
Last Answer : A
Last Answer : The type of dc generator used for arc welding purposes is a Differentially compound generator.
Description : After a black out the emergency generator comes on; On restoring the main supply we are closing the circuit breaker of the main generator without bothering about synchronizing. How is this possible?
Last Answer : There is a power link connection breaker between the main generator and the emergency generator. During black out, this breaker trips. The emergency generator starts and its breaker closes and feeds only ... , there is no paralleling between main and emergency generator. Ask E/O for more details.
Description : Why do we close the switch at 11 o'clock and not at 12 o' clock?
Last Answer : When the synchroscope is approaching 12 o'clock the "slip" (differential) between the sine waves is approaching minimum (slip is zero when the synch'scope is at 12 o'clock) and the voltage differential between ... delay to close, by doing at 11 o'clock, we are achieving closing close to 12 o'clock.
Description : Why we use ac system in India why not dc ?
Last Answer : A:Firstly, the output of power stations comes from a rotary turbine, which by it's nature is AC and therefore requires no power electronics to convert to DC. Secondly it is much easier to ... the sine wave current will naturally tend to zero at some point making the current easier to interrupt.
Description : Can we use ac coils in dc circuit?
Last Answer : Yes with economy resistor in series.
Description : Can we use AC contactor in DC circuit?
Last Answer : Yes, but with adequate de-rating.
Description : when charging a battery we use a DC supply but not an AC supply. Why ?
Last Answer : When power is supplied to the battery, electrolyte inside the battery is divided into positive and negative ions, where ions with similar pole is gained in one side. This reactionʼs flow coincides with direct current.
Description : How can we start-up the 40w tube light with 230v AC/DC without using any choke/Coil?
Last Answer : It is possible by means of Electronic choke. Otherwise it’s not possible to ionize the particles in tube. Light, with normal voltage.
Description : Why can't we store AC in batteries instead of DC ?
Last Answer : Because the direction of the current changes in AC electricity, you cannot directly store the power. Placing a capacitor in an AC circuit has no effect on the alternating flow of the electricity. The only ... is indirectly, by storing DC and then using a power inverter to convert the DC to AC.
Description : I accidently soaked an extension cord. Is it safe to use it again after letting it dry out for awhile?
Last Answer : The plug end is easier to dry out than the socket end get out your blow-dryer and set it to high and blow the end that got wet for a while. That will get most of the water off/out of ... up or sputter. Most modern extension cords are pretty watertight so there shouldn't be any water down the wire.
Description : The use of permanent magnets is. not made in (a) magnetoes (6) energy meters (c) transformers (d) loud-speakers
Last Answer : (c) transformers
Description : Indicatewhich one ofthe followingreasonsforthe use of a groundscreenwith antennasisfalse: a. Impossibility of a good ground connection b. Provision of an earth for the antenna c.Protectionofpersonnelworkingunderneath d. Improvement of the radiation pattern of the antenna
Last Answer : c.Protectionofpersonnelworkingunderneath