MCQOPTIONS
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MCQOPTIONS
This section includes 682 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 251. |
A 500 turns solenoid develops an average induced voltage of 60 V. Over what time interval must a flux change of 0.06 Wb occur to produce such a voltage ? |
| A. | 0.01 s |
| B. | 0.1 s |
| C. | 0.5 s |
| D. | 5 s |
| Answer» D. 5 s | |
| 252. |
Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla. |
| A. | 100 n |
| B. | 400 n |
| C. | 600 n |
| D. | 1000 n |
| Answer» B. 400 n | |
| 253. |
A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla. The force on the conductor will be nearly |
| A. | 50 n |
| B. | 120 n |
| C. | 240 n |
| D. | 480 n |
| Answer» C. 240 n | |
| 254. |
A coil with negligible resistance has 50V across it with 10 mA. The inductive reactance is |
| A. | 50 ohms |
| B. | 500 ohms |
| C. | 1000 ohms |
| D. | 5000 ohms |
| Answer» E. | |
| 255. |
Lenz's law is a consequence of the law of conservation of |
| A. | induced current |
| B. | charge |
| C. | energy |
| D. | induced e.m.f. |
| Answer» D. induced e.m.f. | |
| 256. |
Two coils have self-inductances of 10 H and 2 H, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be |
| A. | 6 h |
| B. | 8 h |
| C. | 12 h |
| D. | 24 h |
| Answer» D. 24 h | |
| 257. |
In case all the flux from the current in coil 1 links with coil 2, the co-efficient of coupling will be |
| A. | 2.0 |
| B. | 1.0 |
| C. | 0.5 |
| D. | zero |
| Answer» C. 0.5 | |
| 258. |
A 200 turn coil has an inductance of 12 mH. If the number of turns is increased to 400 turns, all other quantities (area, length etc.) remaining the same, the inductance will be |
| A. | 6 mh |
| B. | 14 mh |
| C. | 24 mh |
| D. | 48 mh |
| Answer» E. | |
| 259. |
Two coils have inductances of 8 mH and 18 mH and a co-efficient of coupling of 0.5. If the two coils are connected in series aiding, the total inductance will be |
| A. | 32 mh |
| B. | 38 mh |
| C. | 40 mh |
| D. | 48 mh |
| Answer» C. 40 mh | |
| 260. |
Which of the following is unit of inductance ? |
| A. | ohm |
| B. | henry |
| C. | ampere turns |
| D. | webers/metre |
| Answer» C. ampere turns | |
| 261. |
The self inductances of two coils are 8 mH and 18 mH. If the co-efficients of coupling is 0.5, the mutual inductance of the coils is |
| A. | 4 mh |
| B. | 5 mh |
| C. | 6 mh |
| D. | 12 mh |
| Answer» D. 12 mh | |
| 262. |
For a purely inductive circuit which of the following is true ? |
| A. | apparent power is zero |
| B. | relative power is.zero |
| C. | actual power of the circuit is zero |
| D. | any capacitance even if present in the circuit will not be charged |
| Answer» D. any capacitance even if present in the circuit will not be charged | |
| 263. |
An e.m.f. of 16 volts is induced in a coil of inductance 4H. The rate of change of current must be |
| A. | 64 a/s |
| B. | 32 a/s |
| C. | 16 a/s |
| D. | 4 a/s |
| Answer» E. | |
| 264. |
Which of the following circuit elements will oppose the change in circuit current ? |
| A. | capacitance |
| B. | inductance |
| C. | resistance |
| D. | all of the above |
| Answer» C. resistance | |
| 265. |
Which of the following is not a unit of inductance ? |
| A. | henry |
| B. | coulomb/volt ampere |
| C. | volt second per ampere |
| D. | all of the above |
| Answer» C. volt second per ampere | |
| 266. |
The law that the induced e.m.f. and current always oppose the cause producing them is due to |
| A. | faraday |
| B. | lenz |
| C. | newton |
| D. | coulomb |
| Answer» C. newton | |
| 267. |
In case of an inductance, current is proportional to |
| A. | voltage across the inductance |
| B. | magnetic field |
| C. | both (a) and (b) |
| D. | neither (a) nor (b) |
| Answer» C. both (a) and (b) | |
| 268. |
A laminated iron core has reduced eddy-current losses because |
| A. | more wire can be used with less d.c. resistance in coil |
| B. | the laminations are insulated from each other |
| C. | the magnetic flux is concentrated in the air gap of the core |
| D. | the laminations are stacked vertf-cally |
| Answer» C. the magnetic flux is concentrated in the air gap of the core | |
| 269. |
The magnitude of the induced e.m.f. in a conductor depends on the |
| A. | flux density of the magnetic field |
| B. | amount of flux cut |
| C. | amount of flux linkages |
| D. | rate of change of flux-linkages |
| Answer» E. | |
| 270. |
Mutually inductance between two magnetically-coupled coils depends on |
| A. | permeability of the core |
| B. | the number of their turns |
| C. | cross-sectional area of their com-mon core |
| D. | all of the above |
| Answer» E. | |
| 271. |
The direction of incViced e.m.f. can be found by |
| A. | laplace\s law |
| B. | lenz\s law |
| C. | fleming\s right hand rule |
| D. | kirchhoff s voltage law |
| Answer» C. fleming\s right hand rule | |
| 272. |
Air-core coils are practically free from |
| A. | hysteresis losses |
| B. | eddy current losses |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» D. none of the above | |
| 273. |
If current in a conductor increases then according to Lenz's law self-induced voltage will |
| A. | aid the increasing current |
| B. | tend to decrease the amount of cur-rent |
| C. | produce current opposite to the in-creasing current |
| D. | aid the applied voltage |
| Answer» D. aid the applied voltage | |
| 274. |
Both the number of turns and the core length of an inductive coil are doubled. Its self-inductance will be |
| A. | unaffected |
| B. | doubled |
| C. | halved |
| D. | quadrupled |
| Answer» C. halved | |
| 275. |
In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will |
| A. | increase |
| B. | decrease |
| C. | remain the same |
| D. | initially increase and then decrease |
| Answer» C. remain the same | |
| 276. |
Higher the self-inductance of a coil, |
| A. | lesser its weber-turns |
| B. | lower the e.m.f. induced |
| C. | greater the flux produced by it |
| D. | longer the delay in establishing steady current through it |
| Answer» E. | |
| 277. |
Which of the following circuit element stores energy in the electromagnetic field ? |
| A. | inductance |
| B. | condenser |
| C. | variable resistor |
| D. | resistance |
| Answer» B. condenser | |
| 278. |
Laminated cores, in electrical machines, are used to reduce |
| A. | copper loss |
| B. | eddy current loss |
| C. | hysteresis loss |
| D. | all of the above |
| Answer» C. hysteresis loss | |
| 279. |
A ferrite core has less eddy current loss than an iron core because |
| A. | ferrites have high resistance |
| B. | ferrites are magnetic |
| C. | ferrites have low permeability |
| D. | ferrites have high hysteresis |
| Answer» E. | |
| 280. |
The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as |
| A. | self-inductance |
| B. | mutual inductance |
| C. | series aiding inductance |
| D. | capacitance |
| Answer» B. mutual inductance | |
| 281. |
Hysteresis loss least depends on |
| A. | volume of material |
| B. | frequency |
| C. | steinmetz co-efficient of material |
| D. | ambient temperature |
| Answer» E. | |
| 282. |
The unit of reluctance is |
| A. | metre/henry |
| B. | henry/metre |
| C. | henry |
| D. | 1/henry |
| Answer» E. | |
| 283. |
Reciprocal of reluctance is |
| A. | reluctivity |
| B. | permeance |
| C. | permeability |
| D. | susceptibility |
| Answer» C. permeability | |
| 284. |
The unit of retentivity is |
| A. | weber |
| B. | weber/sq. m |
| C. | ampere turn/metre |
| D. | ampere turn |
| Answer» C. ampere turn/metre | |
| 285. |
The property of a material which opposes the creation of magnetic flux in it is known as |
| A. | reluctivity |
| B. | magnetomotive force |
| C. | permeance |
| D. | reluctance |
| Answer» E. | |
| 286. |
Conductance is analogous to |
| A. | permeance |
| B. | reluctance |
| C. | flux |
| D. | inductance |
| Answer» B. reluctance | |
| 287. |
Silicon steel is used in electrical machines because it has |
| A. | low co-ercivity |
| B. | low retentivity |
| C. | low hysteresis loss |
| D. | high co-ercivity |
| Answer» D. high co-ercivity | |
| 288. |
If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be |
| A. | zero |
| B. | small |
| C. | large |
| D. | none of the above |
| Answer» D. none of the above | |
| 289. |
Hard steel is suitable for making permanent magnets because |
| A. | it has good residual magnetism |
| B. | its hysteresis loop has large area |
| C. | its mechanical strength is high |
| D. | its mechanical strength is low |
| Answer» B. its hysteresis loop has large area | |
| 290. |
Those materials are well suited for making permanent magnets which have retentivity and coercivity. |
| A. | low, high |
| B. | high, high |
| C. | high, low |
| D. | low, low |
| Answer» C. high, low | |
| 291. |
In a magnetic material hysteresis loss takes place primarily due to |
| A. | rapid reversals of its magnetisation |
| B. | flux density lagging behind magnetising force |
| C. | molecular friction |
| D. | it high retentivity |
| Answer» E. | |
| 292. |
A material for good magnetic memory should have |
| A. | low hysteresis loss |
| B. | high permeability |
| C. | low retentivity |
| D. | high retentivity |
| Answer» E. | |
| 293. |
The rate of rise of current through an inductive coil is maximum |
| A. | at 63.2% of its maximum steady value |
| B. | at the start of the current flow |
| C. | after one time constant |
| D. | near the final maximum value of current |
| Answer» C. after one time constant | |
| 294. |
Conductivity is analogous to |
| A. | retentivity |
| B. | resistivity |
| C. | permeability |
| D. | inductance |
| Answer» D. inductance | |
| 295. |
Those magnetic materials are best suited for making armature and transformer cores which have permeability and hystersis loss. |
| A. | high, high |
| B. | low, high |
| C. | high, low |
| D. | low, low |
| Answer» D. low, low | |
| 296. |
When both the inductance and resistance of a coil are doubled the value of |
| A. | time constant remains unchanged |
| B. | initial rate of rise of current is doubled |
| C. | final steady current is doubled |
| D. | time constant is halved |
| Answer» B. initial rate of rise of current is doubled | |
| 297. |
Permanent magnets are normally made of |
| A. | alnico alloys |
| B. | aluminium |
| C. | cast iron |
| D. | wrought iron |
| Answer» B. aluminium | |
| 298. |
Relative permeability of vacuum is |
| A. | 1 |
| B. | 1 h/m |
| C. | 1/4ji |
| D. | 4n x 10-\ h/m |
| Answer» B. 1 h/m | |
| 299. |
Point out the wrong statement. Magnetic leakage is undesirable in electric machines because it |
| A. | lowers their power efficiency |
| B. | increases their cost of manufacture |
| C. | leads to their increased weight |
| D. | produces fringing |
| Answer» B. increases their cost of manufacture | |
| 300. |
Permeability in a magnetic circuit corresponds to in an electric circuit. |
| A. | resistance |
| B. | resistivity |
| C. | conductivity |
| D. | conductance |
| Answer» D. conductance | |