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Multiple choice question for engineering

Set 1

1. XMPP Full form is ________
a) Extensible Messaging and Presence Protocol
b) Extensible Module and presence protocol
c) Extensible Messaging and Presence Protocol
d) Extensible Messaging and Presence Protocol

View Answer

Answer: a [Reason:] XMPP is used in IOT which covers XMPP core, XMPP addressing, XMPP server and XMPP client communication. XMPP is the short form of Extensible Messaging and Presence Protocol.

2. XMPP is used for streaming which type of elements?
a) XPL
b) XML
c) XHL
d) MPL

View Answer

Answer: b [Reason:] XMPP is an open protocol for streaming XML elements in order to exchange messages and presence information in close to real time.

3. XMPP creates _________ identity.
a) device
b) email
c) message
d) data

View Answer

Answer: a [Reason:] XMPP creates a device identity also called a Jabber ID. In MQTT, identities are created and managed separately in broker implementations.

4. XMPP supports __________
a) Structured data
b) Foundation
c) Federation
d) Jabber ID

View Answer

Answer: c [Reason:] XMPP supports federation, meaning devices from different manufactures connected to different platforms can talk to each other with a standard communication protocol.

5. Which protocol has a quality of service?
a) XMPP
b) HTTP
c) CoAP
d) MQTT

View Answer

Answer: a [Reason:] MQTT has different levels of quality of services. This flexibility is not available in XMPP.

6. The original transport protocol for XMPP.
a) FCP
b) TCP
c) MCP
d) HCP

View Answer

Answer: b [Reason:] The original and native transport protocol for XMPP is Transmission Control Protocol (TCP), using open ended XML stream over long-lived TCP connections.

7. Which XMPP core describes client server messaging?
a) RFC 6122
b) RFC 4854
c) RFC 6120
d) RFC 3923

View Answer

Answer: c [Reason:] RFC 6120, Extensible Messaging and Presence Protocol (XMPP): core, which describes client-server messaging using two open-ended XML streams.

8. XMPP uses ________ architecture.
a) Decentralized client-server
b) Centralized client-server
c) Message
d) Public/subscriber

View Answer

Answer: a [Reason:] The XMPP uses a decentralized client-server architecture where clients do not talk directly to one another, but there is no central server.

9. XMPP implementation uses ________
a) CoAP
b) Gaming
c) Email
d) Polling

View Answer

Answer: d [Reason:] Most XMPP implementations use polling, or checking for updates only on demand. A protocol called BOSH lets server push messages.

10. XMPP feature such as federation across domains used to implement the Internet of Things.
a) True
b) False

View Answer

Answer: a [Reason:] XMPP feature such as federation across domains, public/subscriber, authentication and its security even for mobile endpoints are being used to implement the Internet of Things.

11. The architecture of the XMPP network is similar to __________
a) Chat box
b) Web browser
c) Gaming
d) Email

View Answer

Answer: d [Reason:] The architecture of the XMPP network is similar to email; anyone can run their own XMPP server and there is no central master server.

12. Does XMPP have text based communication?
a) True
b) False

View Answer

Answer: b [Reason:] Since XML is text based, normal XMPP has a higher network overhead compared to purely binary solution. This issue is being addressed by the experimental XEP -0322.

13. In XMPP In band binary data format is __________
a) High
b) Very high
c) Limited
d) Ultra high

View Answer

Answer: c [Reason:] Binary data must be first base64 encoded before it can be transmitted in band. Therefore, any significant amount of binary data is best transmitted out of band, using in band message to coordinate.

14. IRC stands for __________
a) Internet Reduce Chat
b) Interconnection Relay Chat
c) Internet Relay Chat
d) Interconnect Reduce Chat

View Answer

Answer: c [Reason:] The XMPP extension for multi user chat can be seen a competitor to Internet Relay Chat, although IRC is far simpler, has far fewer features, and is far widely used.

15. SIP stands for ___________
a) Session Initiation Protocol
b) Session Internet Protocol
c) Simple Initiation Protocol
d) Session Internet Protocol

View Answer

Answer: a [Reason:] XMPP has often regarded as a competitor to simple, based on Session Initiation Protocol, as the standard protocol for instant messaging and presence notification.

Set 2

1. __________ performs two functions toward the delivery of the services.
a) Global Scheduler
b) Local Scheduler
c) Device Scheduler
d) IoT Scheduler

View Answer

Answer: a [Reason:] The global Scheduler component is the main and first entry point for service request submitted to the cloud platform. It performs two functions toward the delivery of the services, selection of the sensor and reservation for the needed resources.

2. ___________ manages the meta data of the IoT services.
a) Power
b) Controller
c) Scheduler
d) Package

View Answer

Answer: c [Reason:] Scheduler manages the meta data of the IoT services, signature of the service, sensors used to deliver, and execution parameters.

3. Global scheduler keeps the track of and control the life cycle of IoT services.
a) True
b) False

View Answer

Answer: a [Reason:] Global scheduler keeps the track of and control the life cycle of IoT services. In particular, the lifecycle management services are supported by the scheduler.

4. ___________ service discovers the virtual sensors ability.
a) Register
b) Resource Discovery
c) Unregister
d) Suspend

View Answer

Answer: b [Reason:] Resource recover service discovers the virtual sensors ability. It therefore provides the resources that match the requirements of the given request for the IoT service.

5. ___________ Service is responsible for establishing the requested service with in the cloud database.
a) Suspend
b) Resource Discovery
c) Unregister
d) Register

View Answer

Answer: d [Reason:] Register service is responsible for establishing the requested service with in the cloud database. To this end, it initially identifies and logs all the sensors which are pertinent and or needed for delivering the requested IoT service.

6. For which service the resources allocated for the services are released?
a) Register
b) Resource Discovery
c) Unregister
d) Suspend

View Answer

Answer: c [Reason:] In the scope of the unregister functionality for a given IoT service, the resources allocated for the services are released.

7. _________ service is deactivated and therefore its operation is ceased.
a) Register
b) Resource Discovery
c) Unregister
d) Suspend

View Answer

Answer: d [Reason:] As part of suspend functionality, the service is deactivated and therefore its operation is ceased. However, as part of the suspension the platform does not release the resources associated with the services.

8. _________ service enables the previously suspended services.
a) Enable from suspension
b) Enable
c) Update
d) Registered service status

View Answer

Answer: a [Reason:] Enable from suspension service enables the previously suspended services. The data structures holding the service’s meta data in the cloud are appropriately updated.

9. ________ service allows the enablement of an unregistered service.
a) Enable from suspension
b) Enable
c) Update
d) Registered service status

View Answer

Answer: b [Reason:] Enable service allows the enablement of an unregistered service. In practice this functionality registers the service once again in the platform, through identifying and storing the required sensors.

10. Which service permits the changes to the IoT services?
a) Enable from suspension
b) Enable
c) Update
d) Registered service status

View Answer

Answer: c [Reason:] Update service permits changes to the IoT services. In particular, it allows for the updating of the service’s lifecycle metadata according to the requested changes.

11. Which service provides the lifecycle status of a given IoT service?
a) Enable from suspension
b) Enable
c) Update
d) Registered service status

View Answer

Answer: d [Reason:] Registered service status service provides the lifecycle status of a given IoT service. Detailed information about IoT service is provided.

12. _________ service checks periodically all the enables services.
a) Service updated resources
b) Get service
c) Get available services
d) Update

View Answer

Answer: a [Reason:] Service update resources checks periodically all the enabled services, and identifies those using mobile sensors.

13. _________ service retrieves the description of the registered service.
a) Service updated resources
b) Get service
c) Get available services
d) Update

View Answer

Answer: b [Reason:] Get service retrieves the description of the registered service, that is, the SPARQL description in the case of the OpenIoT open source implementation.

14. Which service returns a list of registered services that are associated with a particular user?
a) Service updated resources
b) Get service
c) Get available services
d) Update

View Answer

Answer: c [Reason:] Get available services return a list of registered services that are associated with a particular user. The various IoT services are registered and established by users of the platform.

15. Which service enables the user to periodically invoke an already defined IoT service?
a) Service updated resources
b) Get service
c) Get available services
d) Poll for the report

View Answer

Answer: d [Reason:] Poll for the report service enables the user to periodically invoke an already defined IoT service within specified time intervals.

Set 3

1. Which type of winding is used in 3-phase shell-type transformer?
a) Circular type
b) Sandwich type
c) Cylindrical type
d) Rectangular type

View Answer

Answer: b [Reason:] In core type of the transformer, winding is done by normal method, while in the shell type transformer, winding is sandwiched between corresponding shells of core material. Hence, it is sandwich type.

2. 3-phase transformers compare to 1-phase transformers ________
a) More economical
b) Easy in construction
c) Easy to construct
d) Easy to handle

View Answer

Answer: a [Reason:] 3-phase transformers are also used to power large motors and other heavy loads. A three-wire three-phase circuit is more economical than an equivalent two-wire single-phase circuit at the same line to ground voltage because it uses less conductor material to transmit a given amount of electrical power.

3. How 3-phase transformers are constructed?
a) A bank of 3 single phase transformers
b) A single 3-phase transformer with the primary and secondary of each phase wound on three legs of a common core
c) Single 3-phase transformer or a bank of 3 1-phase transformers
d) By different method

View Answer

Answer: c [Reason:] #-phase transformers can be either constructed by 2 methods. One is a bank of 3 single phase transformers and another method is a single 3-phase transformer with the primary and secondary of each phase wound on three legs of a common core.

4. Three phase transformer compare to a bank of 3 single phase transformers is ____________
a) Cheaper
b) Costlier
c) More in space
d) Can’t be determined

View Answer

Answer: a [Reason:] 3-phase transformers can be manufactured by 2 methods. The three-phase transformer unit costs about 15% less than that of a bank and furthermore, the single unit occupies less space. There is little difference in reliability.

5. In mines we use _______________
a) a single unit of 3-phase transformer
b) a bank of 3 single phase transformers
c) use of 3-phase transformer is avoided
d) a single unit or a bank

View Answer

Answer: b [Reason:] It is cheaper to carry spare stock of a single-phase rather than a three-phase transformer. In underground use (mines) a bank of single-phase units may be preferred as it is easier to transport these units. The bank also offers the advantage of a de-rated open-delta operation when one single-phase unit becomes inoperative.

6. In three phase bank phases are ___________________
a) the phases are electrically not connected and magnetically independent
b) the phases are electrically not connected and magnetically dependent
c) the phases are electrically connected and magnetically independent
d) the phases are electrically connected and magnetically dependent

View Answer

Answer: c [Reason:] The 3-phase load bank is constructed by so that all three phases are made to be connected with together electrically. By the same time these banks form three magnetic circuits which are independent.

7. Where the tappings are provided in a transformer?
a) At the phase end of LV side
b) At the phase end of HV side
c) At the neutral side end of the HV side
d) At the middle of HV side

View Answer

Answer: d [Reason:] Tappings are provided in order to maintain the terminal voltage across the loads within the permissible specified limits with respect to load variations. Tappings can be provided at phase end or neutral end of HV side. But to maintain magnetic symmetry tappings are preferred in the middle of the winding only.

8. Tappings are on _____________
a) LV side of a transformer
b) HV side of transformer
c) Not on any side
d) On both sides

View Answer

Answer: b [Reason:] Generally, tappings are preferred on HV side, because the HV side is low current-high voltage side, tap changer involves low current interruption and large variations or small steps are possible due to more no of turns.

9. In core type 3-phase transformer flux path chooses how many paths to return?
a) 2
b) Single
c) 3
d) Many

View Answer

Answer: a [Reason:] Flux of each limb in core type uses the other two limbs for its return path with the three-magnetic flux’s in the core generated by the line voltages differing in time-phase by 120 degrees. Thus, the flux in the core remains nearly sinusoidal, producing a sinusoidal secondary supply voltage.

10. Why shell type 3-phase transformer is used in large power transforming applications?
a) Can be made with more height
b) Can be made with less height
c) More height and less height flexibility
d) Due to other reasons

View Answer

Answer: b [Reason:] The shell-type five-limb type three-phase transformer construction is heavier and more expensive to build than the core-type. Five-limb cores are generally used for very large power transformers as they can be made with reduced height.

11. A three-phase transformer generally has the three magnetic circuits interlaced.
a) True
b) False

View Answer

Answer: b [Reason:] A three-phase transformer generally has the three magnetic circuits which are interlaced to give a uniform distribution of the dielectric flux between the high and low voltage windings. The exception is a three-phase shell type transformer. In the shell type of construction, even though the three cores are together, they are non-interlaced.

Set 4

1. Transformer core is generally made of ___________
a) Single block of core material
b) By stacking large number of sheets together
c) Can be made with any of the above method
d) Cannot be determined

View Answer

Answer: b [Reason:] Transformer core experiences eddy current losses when transformer is in the operations. In order to reduce eddy current losses, it is advisable to use large number of sheets laminated from each other are stick together than using one single block.

2. Transformer core is constructed for ______________
a) Providing least effective magnetic linkage between two windings
b) Providing isolation between magnetic linkages of one coil from another
c) Providing most effective magnetic linkage between two windings
d) Cannot be determined

View Answer

Answer: c [Reason:] Transformer core is so chosen that it will provide low reluctance path and will transfer maximum amount of flux from one winding to other, providing most effective magnetic linkage between two windings.

3. Which of the following statements is/are correct?
a) High frequency power supplies are light weight
b) Transformer size gets reduced at high frequency
c) Transformer size is more at higher frequency
d) High frequency power supplies are light weight and transformer size gets reduced at high frequency

View Answer

Answer: d [Reason:] From the induced emf equation of transformer emf is given by E ∝ φf. For same emf, φf = constant φ1f1 = φ2f2 i.e. B1A1f1 = B2A2f2. For constant flux density B1 = B2. A1f1 = A2f2. For high frequency f2 > f1, A2 < A1. Thus, at high frequencies transformer size get reduced and also light weight.

4. Transformer operating at 25-400 Hz frequency contain core made of _____________
a) Highly permeable iron
b) Steel alloy
c) Air core
d) Highly permeable iron and Steel alloy

View Answer

Answer: d [Reason:] When core is made of highly permeable iron or steel alloy (cold-rolled, grain oriented sheet steel). This transformer is generally called an iron-core transformer. Transformers operated from 25–400 Hz are invariably of iron-core construction.

5. In various radio devices and testing instruments we use ______________
a) Iron core transformer
b) Air core transformer
c) W/O core transformer
d) Any transformer can be used

View Answer

Answer: a [Reason:] In special cases, the magnetic circuit linking the windings may be made of nonmagnetic material, in which case the transformer is referred to as an air-core transformer. The air-core transformer is of interest mainly in radio devices and in certain types of measuring and testing instruments.

6. Which type of flux does transformer action need?
a) Constant magnetic flux
b) Increasing magnetic flux
c) Alternating magnetic lux
d) Alternating electric flux

View Answer

Answer: c [Reason:] The energy transfer in a transformer, is from one winding to another, entirely through magnetic medium it is known as transformer action. Therefore, transformer action requires an alternating or time varying magnetic flux in order to transfer power from primary side to secondary side. Since induced emf in the winding is due to flux linkage.

7. Different core construction is required for core type and shell type transformer.
a) True
b) False

View Answer

Answer: a [Reason:] In the “closed-core” type transformer, the primary and secondary windings are wound outside and surround the core ring. In the “shell type” transformer, the primary and secondary windings pass inside the steel magnetic circuit (core) which forms a shell around the windings.

8. There is only one magnetic flux path in the circuit. The transformer is definitely ________________
a) Core type
b) Shell type
c) Can be any of the above
d) Depends on other parameters

View Answer

Answer: a [Reason:] In core type transformer, winding is placed on two core limbs, while in case of shell type transformer, winding is placed on mid arm of the core. Other limbs will be used as mechanical support. Core type transformers have only one magnetic flux path.

9. Which of the following is correct statement?
a) Core type transformer has more output than shell type
b) Core type transformer has higher efficiency compare to shell type
c) Core type transformer has lower efficiency than shell type
d) Can’t predict

View Answer

Answer: c [Reason:] In core type winding is surrounded with considerable part of core whereas in shell type core is surrounded with considerable part of winding of transformer. In core type output is less, because of losses. In shell type transformer output is high because of less loss, thus efficiency will be more in case of shell transformer.

10. Core type transformer is with ____________________
a) Large size
b) Small size
c) High voltage
d) Everywhere

View Answer

Answer: a [Reason:] Core type is very useful when we need large size of the transformer with operation at low voltage. While shell type transformer is very useful when we need small size high voltage. Cooling is more in core type.

11. Which of the following is the correct statement?
a) Shell type has more mechanical protection
b) Cooling is more in shell type
c) In core type sandwiched wiring is used
d) In core type concentric winding is used

View Answer

Answer: d [Reason:] Shell type has less mechanical protection to coil while Core type has better mechanical protection to coil. Core type is easy to repair and maintain. In core type transformer concentric cylindrical winding are used. In shell type transformer sandwiched winding are used.

12. What is the purpose of providing an iron core in a transformer?
a) Provide support to windings
b) Reduce hysteresis loss
c) Decrease the reluctance of the magnetic path
d) Reduce eddy current losses

View Answer

Answer: c [Reason:] Iron core is used in a transformer to carry flux from one winding to another winding, so there should be minimum opposition to flux passing through iron core. Hence, transformer function is to decrease the reluctance of magnetic path.

13. What is the thickness of laminations used in a transformer?
a) 0.1 mm to 0.5 mm
b) 4 mm to 5 mm
c) 14 mm to 15 mm
d) 25 mm to 40 mm

View Answer

Answer: a [Reason:] Laminations are made to reduce the eddy currents and is made of thin strips. Generally, the steel transformer lamination range for 50 Hz varies from 0.25mm to 0.5mm, if it is a 60 Hz transformer then it ranges from 0.17–0.27mm.

Set 5

1. In the transformer which of the following winding has got more cross-sectional area?
a) Copper winding
b) Steel winding
c) Aluminium winding
d) Iron winding

View Answer

Answer: a [Reason:] The wire used for carrying current in a transformer winding is either copper or aluminium. While aluminium wire is lighter and less expensive than copper wire, a larger cross-sectional area of conductor must be used to carry the same amount of current as with copper.

2. Primary winding of a transformer ______________
a) Is always a high voltage winding
b) Is always a low voltage winding
c) Could either be a low voltage or high voltage winding
d) Cannot be determined

View Answer

Answer: c [Reason:] Primary winding used in a transformer, can be at higher or lower voltage potential, depending on the number of turns with secondary winding. For step up and step-down transformers primary winding will be at lower and higher potential respectively.

3. Which winding has more number of turns?
a) Low voltage winding
b) High voltage winding
c) Primary winding
d) Secondary winding

View Answer

Answer: b [Reason:] High voltage winding always has a large number of turns, as voltage is directly proportional to the number of turns. If large numbered winding is present on primary side then the transformer is step down transformer.

4. Part of the transformer which undergoes most damage from overheating is ___________
a) Iron core
b) Copper winding
c) Winding insulation
d) Frame or case

View Answer

Answer: c [Reason:] Copper windings carry current through them. The heat loss producing in any winding carrying current is proportional to the square of the current passing through it multiplied with resistance. For large transformers, current is very high, so heating causes most of the damage to insulation material.

5. If a transformer is continuously operated the maximum temperature rise will occur in ___________
a) Core
b) Windings
c) Tank
d) Cannot be determined

View Answer

Answer: b [Reason:] Copper windings carry currents in a transformer. The loss in form of heat in copper winding carrying current is proportional to the square of the current passing through them multiplied by the resistance of the winding. This loss is dissipated in heat and corresponding temperature rise.

6. If secondary number of turns are higher then, transformer is called _________
a) Step-down
b) Step-up
c) One-one
d) Autotransformer

View Answer

Answer: b [Reason:] When secondary number of turns are higher compare to primary, voltage induced in secondary windings will obviously high. Thus, this transformer is used for stepping up the output voltage by keeping frequency constant.

7. If primary number of turns are higher then, transformer is called _________
a) Step-down
b) Step-up
c) One-one
d) Autotransformer

View Answer

Answer: a [Reason:] When primary number of turns are higher compare to secondary, voltage induced in secondary windings will obviously low compare to primary. Thus, this transformer is used for stepping down the output voltage by keeping frequency constant.

8. If a transformer is having equal number of turns at primary and secondary then transformer is called as _______________
a) Step-down
b) Step-up
c) One-one
d) Autotransformer

View Answer

Answer: c [Reason:] A transformer is having equal number of turns at primary and secondary then transformer is called as one-one transformer. This transformer have turns ratio equal to 1, so is the voltage ratio for the one-one transformer.

9. One to one transformers are used because ______________
a) To isolate any part of circuit electrically
b) To get more voltage at secondary
c) To get less voltage at secondary
d) To reduce losses, present in circuit

View Answer

Answer: a [Reason:] In one to one transformers, we have same number of turns in primary and in secondary. So, increasing/ reducing voltage is not possible. They are generally used to isolate one part of circuit from another part of circuit, electrically.

10. Same type and kind of insulations are not used in all types of transformers.
a) True
b) False

View Answer

Answer: a [Reason:] The windings of huge power transformers use conductors with heavier insulation and are assembled with greater mechanical support and the winding layers are insulated from each other, this is known as minor insulation for which pressed board or varnished cloth is used. While for major insulation and insulating cylinders, they are made of specially selected pressed board or synthetic resin bounded cylinders, is used between LV and core and LV and HV.

11. Sandwiched type of winding is used in ____________
a) In all transformers
b) In core type transformers
c) In shell type transformers
d) In all transformers except shell and core type transformers

View Answer

Answer: c [Reason:] According to the construction of transformers core type transformers don’t require sandwiched wiring. While, in the shell type transformer, the primary and secondary windings pass inside the steel magnetic circuit (core) which forms a shell around the winding.

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