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Worksheets301-400
Total questions: 100
Worksheet time: 50mins
Name
Class
Date
1.
301. Two inductor coils in very close proximity; if one of the coils is rotated 90 degrees slowly away from the other the mutual inductance (Level 1)
a)
a) Decreases
b)
b) Remains the same
c)
c) Increases.
2.
302. Two inductor coils in very close proximity; If the angle is 0 degree the magnetic flux which is generated by coil 1 will hit coil 2 in an optimal way. Coil 2 will have: (Level 2)
a)
a) A no voltage.
b)
b) The maximum possible voltage
c)
c) A lower voltage
3.
303. Two inductor coils in very close proximity; If the angle is 45 degree the magnetic flux which is generated by coil 1 will hit coil 2 in an optimal way. Coil 2 will have: (Level 2)
a)
a) A no voltage.
b)
b) The maximum possible voltage
c)
c) A lower voltage
4.
304. Which statement is correct? (Level 1)
a)
a) Current transformers allow the measurement of AC currents without breaking the current−carrying leads
b)
b) Current transformers allow the measurement of AC voltage without breaking the current−carrying leads
c)
c) Current transformers allow the measurement of DC voltage without breaking the current−carrying leads
5.
305. Which methods are applied to control the speed of DC machines in practice? (Level 1)
a)
a) Voltage control and Field Control
b)
b) Voltage control
c)
c) Field Control
6.
306. The stationary part of a electrical machine is (Level 1)
a)
a) Magnetic flux
b)
b) Stator
c)
c) Rotor
7.
307. The rotating part of a electrical machine is (Level 1)
a)
a) Magnetic flux
b)
b) Stator
c)
c) Rotor
8.
308. The induced voltage increases proportional to: (Level 2)
a)
a) Magnetic field strength, speed of movement and the length of the conductor
b)
b) Speed of movement, the length of the conductor
c)
c) Magnetic field strength, speed of movement
9.
309. How many part the rotor of a electrical machine has? (Level 2)
a)
a) 1
b)
b) 3
c)
c) 2
10.
310. In a DC motor, the stator's magnetic field, due to armature reaction, moves (Level 2)
a)
a) Into alignment with the GNA
b)
b) In the same direction of rotation of the armature
c)
c) In the opposite direction of rotation of the armature
11.
311. Which statement is correct? (Level 2)
a)
a) The DC shunt−wound motor is used whenever a constant speed at various loads is required,
b)
b) The DC shunt −wound motor is used whenever a constant speed at various loads is not required,
c)
c) The DC shunt−wound motor is used whenever a high power is required,
12.
312. Which statement is correct? (Level 1)
a)
a) The stator of a DC machine has a steel ring (yoke), the main poles made of sheet metal with pole core
b)
b) The stator of a DC machine has the main poles made of sheet metal with pole core, pole shoe and the excitation winding.
c)
c) The stator of a DC machine has a steel ring (yoke), the main poles made of sheet metal with pole core and pole shoe and the excitation winding.
13.
313. Commutating poles are connected (Level 2)
a)
a) In parallel with the armature and hence oppose the armature cross field
b)
b) In series with the armature and hence oppose the armature cross field
c)
c) In series with the armature and stator
14.
314. The series−wound machine basically consists of (Level 1)
a)
a) The stator with the excitation winding, the rotor with the armature winding and the carbon brushes
b)
b) The stator with the excitation winding, the rotor with the armature winding
c)
c) The rotor with the armature winding, the carbon brushes
15.
315. What is the meaning of peak value? (Level 1)
a)
a) The positive maximum value which a sine curve can assume
b)
b) The positive or negative maximum value which a sine curve can assume
c)
c) The negative maximum value which a sine curve can assume
16.
316. The peak power is calculated by: (Level 2)
a)
a) Multiplying the peak voltage Upeak with the peak current Ipeak
b)
b) Average the peak voltages Upeak
c)
c) Average the peak current Ipeak
17.
317. Peak−to−peak value means: (Level 2)
a)
a) Negative maximum value of a sine curve
b)
b) Positive maximum value of a sine curve
c)
c) The value measured between positive maximum value and negative maximum value of a sine curve
18.
318. What is the definition of Triangular Waves? (Level 1)
a)
a) Triangular Waves are given if the voltage increases linearly and, if a certain level is achieved, decreases linearly.
b)
b) Triangular Waves are given if the voltage decreases linearly and, if a certain level is achieved, decreases linearly.
c)
c) Triangular Waves are given if the voltage increases linearly and, if a certain level is achieved, increases linearly.
19.
319. What is the definition of Triangular Waves? (Level 1)
a)
a) Triangular Waves are given if the current periodically changes between two values
b)
b) Triangular Waves are given if the voltage periodically changes between two values
c)
c) Triangular Waves are given if the voltage no changes
20.
320. If the magnetic wheel of a bipolar device (one pole pair) rotates 50 times per second, (Level 2)
a)
a) An AC with a frequency of f = 5 Hz is generated
b)
b) An AC with a frequency of f = 500 Hz is generated
c)
c) An AC with a frequency of f = 50 Hz is generated
21.
321. A sine wave has 5 amps RMS value. What is the peak value? (Level 2)
a)
a) 7.07 amps.
b)
b) 6.37 amps.
c)
c) 10 amps.
22.
322. A sine wave has 10 voltage the peak value. What is RMS value? (Level 2)
a)
a) 14,14 V
b)
b) 7.07 V
c)
c) 10 V
23.
323. The RMS power is calculated by (Level 1)
a)
a) Multiplying the RMS voltage V with the RMS current I
b)
b) Multiplying the Upeak voltage V with the RMS current I
c)
c) Multiplying the RMS voltage V with the Ipeak
24.
324. The symbol for frequency is (Level 1)
a)
a) H
b)
b) F
c)
c) B
25.
325. A heating device applied to 240 V consumes 3 A. What is the resistance? (Level 1)
a)
a) 80 Ω
b)
b) 90 Ω
c)
c) 70 Ω
26.
326. In a coil with an inductive reactance of XL = 30 Ohm a current of I = 2 A flows. What voltage occurs on the inductive reactance? (Level 1)
a)
a) 40 V
b)
b) 60 V
c)
c) 50 V
27.
327. An ideal coil with an inductance of L = 200 mH is applied to an AC voltage of U = 220, f = 50 Hz, What is the inductive reactance? (Level 2)
a)
a) 31,4 Ω
b)
b) 6,28 Ω
c)
c) 62,8 Ω
28.
328. An ideal coil with an inductance of L = 200 mH is applied to an AC voltage of U = 220, f = 50 Hz, What current builds up? (Level 2)
a)
a) 3,5 A
b)
b) 0.291666666666667
c)
c) 35 A
29.
329. The symbol for reactive power is (Level 1)
a)
a) P
b)
b) Q
c)
c) A
30.
330. The symbol for capacitive reactive power is (Level 1)
a)
a) P
b)
b) Q
c)
c) Qc
31.
331. The reactive power is measured in (Level 1)
a)
a) Var
b)
b) W
c)
c) KW
32.
332. The symbol for apparent power is (Level 1)
a)
a) P
b)
b) S
c)
c) Var
33.
333. The apparent power is measured in (Level 1)
a)
a) Var
b)
b) KW
c)
c) Volt-Ampere [VA]
34.
334. A pure capacitor, inductor and resistor are connected in series and the voltage drops across each are 10V and the total current flowing in the circuit is 1A. How much true power is the circuit consuming? (Level 1)
a)
a) 10W
b)
b) 30VA
c)
c) 30W
35.
335. A coil that has an effective resistance of 12 Ohms and is applied to an AC voltage of 36 V at 50 Hz has a current consumption of 1 A. Calculate the impedance. (Level 2)
a)
a) 18 Ω
b)
b) 36 Ω
c)
c) 3,6 Ω
36.
336. A coil that has an effective resistance of 12 Ohms and is applied to an AC voltage of 36 V at 50 Hz has a current consumption of 1 A. Calculate the inductive reactance. (Level 2)
a)
a) 35 Ω
b)
b) 40 Ω
c)
c) 33,9 Ω
37.
337. A coil that has an effective resistance of 12 Ohms and is applied to an AC voltage of 36 V at 50 Hz has a current consumption of 1 A. Calculate the effective voltage. (Level 2)
a)
a) 11,88 V
b)
b) 12 V
c)
c) 24 V
38.
338. A coil that has an effective resistance of 12 Ohms and is applied to an AC voltage of 36 V at 50 Hz has a current consumption of 1 A. Calculate the reactive voltage (Level 2)
a)
a) 25 V
b)
b) 33,9 V
c)
c) 40 V
39.
339. A capacitor with a capacitance with C = 10 µF is connected to an AC voltage source with U = 220 V, f = 50 Hz, What value is the capacitive reactance of the capacitor? (Level 2)
a)
a) XC= 318 Ω
b)
b) XC= 381 Ω
c)
c) XC= 636 Ω
40.
340. A capacitor with a capacitance with C = 10 µF is connected to an AC voltage source with U = 220 V, f = 50 Hz, What value is the current input of the capacitor? (Level 2)
a)
a) 3,46 A
b)
b) 0,692 A
c)
c) 0,173 A
41.
341. Generally, a transformer consists of: (Level 1)
a)
a) Two coils and an iron core
b)
b) Two cores and a coil
c)
c) Two cores and an iron core
42.
342. The number of windings of the transformer's input coil is (Level 1)
a)
a) N1/N0
b)
b) N1
c)
c) N2
43.
343. The number of windings of the transformer's output coil is (Level 1)
a)
a) N1/N1
b)
b) N1
c)
c) N2
44.
344. The turns ratio of transformer is calculated with this formula (Level 1)
a)
a) N1/N2
b)
b) N3
c)
c) N2
45.
345. A transformer has an input voltage of 220 V AC. The self-induced voltage in the primary coil is 215.5 V. It opposes the input voltage. In the primary coil, the resistance of the windings is 3 Ω. What is the no-load current of the transformer? (Level 2)
a)
a) 1A
b)
b) 1.5A
c)
c) 2A
46.
346. A transformer has an input voltage of 220 V AC. The self-induced voltage in the primary coil is 215.5 V. It opposes the input voltage. In the primary coil, the resistance of the windings is 3 Ω. What is the current without self-induced voltage? This will happen when the voltage is a DC voltage. (Level 2)
a)
a) 71,6A
b)
b) 72,5A
c)
c) 73,3A
47.
347. An AC transformer converts a voltage of 220 V to 12 V. The secondary coil has 100 turns. How many turns must the primary winding have? (Level 2)
a)
a) 1833
b)
b) 958
c)
c) 1000
48.
348. The secondary winding of a transformer with 60 turns consumes a current of 10 A. How many amperes consumes a primary winding with 1200 turns? (Level 2)
a)
a) 1A
b)
b) 0,5 A
c)
c) 2A
49.
349. A transformer is used to supply four motors. Each motor gives a power of 5 kW. The power factor of the motors is 0.9. What is the minimum nominal power output of the transformer? (Level 2)
a)
a) 20 W
b)
b) 25 W
c)
c) 22,22 W
50.
350. The short circuit voltage of a transformer is (Level 1)
a)
a) A reference for the change of the output voltage when the load increases
b)
b) A reference for the change of the output voltage when the load decreases
c)
c) A reference for the change of the output voltage when the load no change
51.
351. The symbol for the resonance frequency is (Level 1)
a)
a) Fres
b)
b) F
c)
c) Fr
52.
352. A series resonant circuit consists of (Level 1)
a)
a) A coil and a capacitor connected in parallel
b)
b) A coil and a capacitor connected in series
c)
c) Tow coils and a capacitor connected in series
53.
353. In series resonance, which are condition for resonances? (Level 1)
a)
a) XL = XC
b)
b) UL = UC
c)
c) XL = XC; UL = UC
54.
354. A band −stop filter consists of (Level 1)
a)
a) A high−pass filter and a low−pass filter in parallel
b)
b) A high−pass filter and a low−pass filter in series
c)
c) Tow high−pass filters in parallel
55.
355. A band−pass filter consists of (Level 1)
a)
a) A high−pass filter and a low−pass filter in parallel
b)
b) A high−pass filter and a low−pass filter in series
c)
c) Tow high−pass filters in parallel
56.
356. The synchronous machines have (Level 1)
a)
a) A constant ratio of rotation speed and frequency.
b)
b) A constant ratio of rotation speed
c)
c) A constant of frequency.
57.
357. The AC generators of airplanes supply an AC voltage with a frequency of 400 Hz. How many pole pairs are necessary in a generator of a B737 which is driven at 6000 rpm? (Level 2)
a)
a) 2
b)
b) 4
c)
c) 6
58.
358. The advantages of a brushless alternator are (Level 1)
a)
a) Lower maintenance cost, High stability and consistency of output
b)
b) High stability and consistency of output, better performance at high altitudes
c)
c) Lower maintenance cost, High stability and consistency of output, better performance at high altitudes
59.
359. A two-phase generator provides 220 V on both the lines.
The phase-to-phase voltage is (Level 2)
a)
a) 311 V
b)
b) 220 V
c)
c) 155 V
60.
360. An alternating current generator is operating at 40 kVA in a circuit with a power factor of 0.9. The real power is (Level 1)
a)
a) 40 kVA
b)
b) 36 kVA
c)
c) 50 kVA
61.
361. The two factors which govern the output frequency of an AC generator are the (Level 1)
a)
a) Strength of the stator field flux and number of poles
b)
b) Speed of rotation of the rotor and the stator field flux strength
c)
c) The number of poles (in pairs) and the rotor RPM
62.
362. In a delta-connected generator (Level 2)
a)
a) Line volts = phase volts, line current = root 3 times phase current
b)
b) Line voltage = root 3 times phase voltage, line current = phase current
c)
c) Line volts = phase volts, line current = phase current divided by root 3.
63.
363. The permanent magnet in an A.C generator induces (Level 2)
a)
a) A.C. in the main generator
b)
b) A.C. in the exciter generator
c)
c) D.C. in the exciter generator
64.
364. If the phase voltage in a star connected generator is 200V what will be the line voltage? (Level 1)
a)
a) 220 V
b)
b) 282 V
c)
c) 346 V
65.
365. A generator is labeled as having 115V/200V, 20A and PF 0.8. What is the apparent power in each line that the generator can produce? (Level 2)
a)
a) 4 kVA
b)
b) 2,3 kVA
c)
c) 3,2 kVA
66.
366. AC generators are rated in (Level 1)
a)
a) KVARs
b)
b) KVA
c)
c) KW
67.
367. There are actually three separate generators within one case (Level 2)
a)
a) The permanent magnet generator, the exciter generator, a rotating rectifier
b)
b) The exciter generator, the main generator, a GCU
c)
c) The permanent magnet generator, the exciter generator, the main generator
68.
368. A 30 KVA rated generator has a power factor of 0.8. What is its maximum consistent power? (Level 1)
a)
a) 24 KW
b)
b) 30 KW
c)
c) 37.5 KW
69.
369. The voltage induced in the stator of an AC generator is produced by (Level 1)
a)
a) An alternating field
b)
b) A rotating magnetic field
c)
c) A fixed magnetic field
70.
370. Permanent magnets in an AC generator are (Level 2)
a)
a) To rectify the current
b)
b) To control the frequency
c)
c) To provide initial excitation
71.
371. In Operation of an Aircraft Generator, If the voltage is too low (Level 2)
a)
a) The GCU will increase the exciter field current
b)
b) The GCU will increase magnetic field
c)
c) The GCU will reduce the exciter field current
72.
372. A synchronous machine consists of (Level 1)
a)
a) A stator with a winding and a rotor which also carries a winding
b)
b) A stator with a winding
c)
c) rotor which also carries a winding
73.
373. The rotating field is generated by (Level 1)
a)
a) The PMG
b)
b) The rotary current which is connected to the stator windings.
c)
c) The stator windings.
74.
374. The synchronous motor is used to (Level 1)
a)
a) Achieve a constant current
b)
b) Achieve a constant voltage
c)
c) Achieve a constant rotational speed
75.
375. An AC motor which rotates at the same speed as supply frequency is called (Level 1)
a)
a) A synchronous motor
b)
b) A universal machine
c)
c) An induction motor
76.
376. A three-phase motor has the windings (Level 2)
a)
a) 180° apart
b)
b) 120° apart
c)
c) 90° apart
77.
377. A capacitor in a single phase AC motor is to (Level 2)
a)
a) Block DC
b)
b) Prevent spikes
c)
c) Provide a phase shift
78.
378. If the motor must have a high starting torque, how to start the motor? (Level 2)
a)
a) Need a second capacitor (starting capacitor CA) is connected in parallel to the running capacitor during the start−up
b)
b) Need a second capacitor (starting capacitor CA) is connected in series to the running capacitor during the start−up
c)
c) Only need a running capacitor during the start−up
79.
379. Calculate the speed of a 400 Hz, 4 pole machine (Level 2)
a)
a) 12,000 rpm
b)
b) 6000 rpm
c)
c) 8000 rpm
80.
380. The stator consists of (Level 1)
a)
a) A housing and carbon brushes
b)
b) A laminated core with slots and a commulator
c)
c) A housing and a laminated core with slots
81.
381. The speed of an AC motor can be affected by the (Level 2)
a)
a) Pairs of poles
b)
b) Armature current
c)
c) Field current
82.
382. The principal characteristic of a synchronous motor is (Level 1)
a)
a) It rotates at a speed that is synchronised with the applied dc current
b)
b) It rotates at a speed that is synchronised with the applied ac current
c)
c) It must have a synchronised 3 phase supply to operate
83.
383. What is the purpose of the capacitor used in a single phase AC motor? (Level 2)
a)
a) Smoothing
b)
b) Changing direction of motor
c)
c) Provides a high starting torque
84.
384. The rotational speed of such a motor depends on (Level 1)
a)
a) The frequency of the supply voltage and the amount of pole pairs.
b)
b) The frequency of the supply voltage
c)
c) The amount of pole pairs.
85.
385. Why the single−phase AC motor with only one winding cannot start by itself? (Level 2)
a)
a) Because the single−phase AC voltage has a great inertial force
b)
b) Because the single−phase AC voltage only generates one changing magnetic field
c)
c) Because the single−phase AC voltage generates many changing magnetic fields
86.
386. What is purpose of a A single phase synchronous motor's commutator? (Level 1)
a)
a) To adjust the current direction in the rotor winding
b)
b) To adjust the current direction in the stator
c)
c) To provide the current direction in the rotor winding
87.
387. Where does current inside the rotor windings come from? (Level 2)
a)
a) Rotor bar
b)
b) The rotating magnetic field of the stator
c)
c) Main Pole
88.
388. Diodes are: (Level 1)
a)
a) Conductors,
b)
b) Semi-conductors
c)
c) Insulators
89.
389. For the intrinsic conductivity of diodes (Level 1)
a)
a) At 0 degrees Kelvin, a semiconductor is a non-conductor
b)
b) At 0 degrees Celsius, a semiconductor is a non-conductor
c)
c) At 0 degrees Kelvin, a semiconductor is a conductor
90.
390. A junction diode (Level 1)
a)
a) Is similar to a vacuum diode but cannot rectify
b)
b) Has one p-n junction
c)
c) Can handle only very small currents
91.
391. In a semiconductor junction diode, electrons are the minority carriers. (Level 1)
a)
a) Within the P region
b)
b) Within the N region
c)
c) In both the N and P regions
92.
392. Forward voltage of a silicon diode is. (Level 1)
a)
a) 1.7V
b)
b) 0.7V
c)
c) 0.3V
93.
393. To function, i.e. conduct, a junction diode made of silicon requires a forward bias of at least (Level 2)
a)
a) 0.2 V
b)
b) 1.41 V
c)
c) 1 V
94.
394. If forward bias is increased from zero on a p-n junction, a rapid increase in current flow for a relatively small increase in voltage occurs. (Level 2)
a)
a) When the flow of minority carriers is sufficient to cause an avalanche breakdown
b)
b) When the depletion layer becomes larger than the space charge area
c)
c) Only after the forward bias exceeds the potential barrier
95.
395. When a diode is forward biased the (Level 2)
a)
a) Positive lead is connected to both N and P type
b)
b) Positive lead is connected to the P type and negative to the N type.
c)
c) Positive lead is connected to the N type and negative to the P type
96.
396. The micro diodes are: (Level 2)
a)
a) Primarily used for electrical power supply devices
b)
b) Mainly used in communication technology
c)
c) Used in rectifier circuits for large power outputs
97.
397. The rectifier diodes are: (Level 2)
a)
a) Primarily used for electrical power supply devices
b)
b) Mainly used in communication technology
c)
c) Used in rectifier circuits for large power outputs
98.
398. The terminal of transistor with an arrow is named (Level 1)
a)
a) Base
b)
b) Collector
c)
c) Emitter
99.
399. In a NPN transistor the P is the (Level 1)
a)
a) Collector
b)
b) Emitter
c)
c) Base
100.
400. Which layer of transistor is called the emitter? (Level 1)
a)
a) First layer
b)
b) Middle layer
c)
c) Last layer
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