Questions and answers for exam Preparation

MCQs

Total Questions : 480 | Page 44 of 48 pages

Question 431. For a pure capacitor:

ac current and voltage are exactly in phase
ac current leads the voltage by 90 degree
ac current is converted to dc voltage
ac current lags the voltage by 90 degree
None of the above

Discuss Question

Answer: Option B. -> ac current leads the voltage by 90 degree

Question 432. In a pure inductor:

ac current leads the voltage by 90 degree
ac current and voltage are exactly in phase
ac current lags the voltage by 90 degree
ac current is converted to dc voltage
None of the above

Discuss Question

Answer: Option C. -> ac current lags the voltage by 90 degree

Question 433. The component that forms the electrical connection between the rotating coil of wire in a motor and the external source of electrical energy is called the:

rotor
armature
battery
commutator
None of the above

Discuss Question

Answer: Option D. -> commutator

Question 434. Waveforms are graphs that show:

frequency on the vertical axis and amplitude on the horizontal axis
amplitude on the vertical axis and frequency on the horizontal axis
amplitude on the vertical axis and the passage of time on the horizontal axis
the passage of time on the vertical axis and amplitude on the horizontal axis
None of the above

Discuss Question

Answer: Option C. -> amplitude on the vertical axis and the passage of time on the horizontal axis

Question 435. When the collector current increases, what does the current gain do?

decreases
stays the same
increases
any of the above
None of the above

Discuss Question

Answer: Option C. -> increases

Question 436. Which one of the following statements best describes magnetic hysteresis?

Hysteresis is the amount of magnetic flux that is not confined to the core material of an electromagnet
Hysteresis is most apparent when a steady amount of current is lowing through the coil of an electromagnet
Hysteresis is most apparent when the current through the coil of an electromagnet changes frequently
Hysteresis is most apparent when the core material is saturated
None of the above

Discuss Question

Answer: Option C. -> Hysteresis is most apparent when the current through the coil of an electromagnet changes frequently

Question 437. Which one of the following phrases best describes residual magnetism?

Magnetism that remains in the core of an electromagnet after the current through the coil is turned off
The force of attraction between the poles of a permanent and temporary magnetic field
The amount of magnetic flux that is not confined to the core material of an electromagnet
The circular magnetic field that surrounds a conductor carrying a current
None of the above

Discuss Question

Answer: Option A. -> Magnetism that remains in the core of an electromagnet after the current through the coil is turned off

Question 438. Household light bulbs have a given power rating, and they operate at 120 V. Which one of the following equations most directly provides the current rating of these light bulbs?

P = I2R
P = IE
P = E2/R
I = P/E
None of the above

Discuss Question

Answer: Option D. -> I = P/E

Question 439. A transformer has a primary voltage of 120 V rms and a secondary voltage of 25 V rms. If the secondary current is 1A rms, what is the primary current?

7.8 mA
208 mA
200 mA
300 mA
None of the above

Discuss Question

Answer: Option B. -> 208 mA

Question 440. Which one of the following phrases most accurately describes a purely inductive circuit?

Resistances provide the only opposition to current flow
Inductive reactance provides the only opposition to current flow
Combinations of resistance and inductive reactance provide any opposition to current flow
The ac voltage lags the current by 90 degree
None of the above

Discuss Question

Answer: Option B. -> Inductive reactance provides the only opposition to current flow