A level AC Theory Quiz 1

16 Questions

Quiz Description

In this quiz, we will be looking at AC Theory which stands for Alternating current theory. Alternating current is used in the industry of transportation and production of electricity. We have seen that almost every household in the world is powered by AC. AC is therefore a more popular current when it comes to powering electric motors, which are devices that convert electrical energy into mechanical energy. You will find so many interesting questions in Physics here which will help prepare you for any challenge on AC theory.

To begin, let us ask ourselves, what is AC current?

Alternating Current (AC) is simply a type of electrical current, in which the direction of flow of the electrons switches back and forth at regular intervals or cycles.

Therefore AC theory is concerned with the mathematical analysis of the steady-state behavior of electrical circuits in which the currents and voltages vary periodically with respect to time. Contrary to AC current, we have DC (Direct current) which flows only in one direction. Examples of products that are produced using AC are flashlights, cell phones, and even modern-day televisions.

Many quizzes on other subjects can be found by clicking here. For more knowledge on current, Check on Current E..Now test yourself by taking the quiz, which will teach you even more.
Good luck! 

1:

The series and parallel resonance on L-C circuit' differs in that


Correct
  • 1:
    Series resistance needs a low-resistance source for sharp rise in current
  • 2:
    Series resonance needs a high-resistance source for sharp increase in current
  • 3:
    Parallel resonance needs a low-resistance source for a sharp increase in impedance
  • 4:
    Parallel resonance needs a low-resistance source for a sharp rise in line current
2:

In each of the three coils of a three phase generator, an alternating voltage having an r.m.s. value of 220 V is induced. Which of the following values is indicated by the voltmeters?


Correct
  • 1:
    220 V
  • 2:
    220 √3 V
  • 3:
    220/√3 V
  • 4:
    None of the above
3:

In a highly capacitive circuit the


Correct
  • 1:
    Apparent power is equal to the actual power
  • 2:
    Reactive power is more than the apparent power
  • 3:
    Reactive power is more than the actual power
  • 4:
    Actual power is more than its reactive power
4:

The power factor at resonance in R-L-C parallel circuit is


Correct
  • 1:
    Zero
  • 2:
    0.08 lagging
  • 3:
    0.8 leading
  • 4:
    Unity
5:

 In a R-L-C circuit


Correct
  • 1:
    Power is consumed in resistance and is equal to IR
  • 2:
    Exchange of power takes place between inductor and supply line
  • 3:
    Exchange of power takes place between capacitor and supply line
  • 4:
    All above are correct
6:

In an AC. circuit, a low value of kVAR compared with kW indicates


Correct
  • 1:
    Low efficiency
  • 2:
    High power factor
  • 3:
    Unity power factor
  • 4:
    Maximum load current
7:

Which of the following statements pertains to resistors only?


Correct
  • 1:
    Can dissipate considerable amount of power
  • 2:
    Can act as energy storage devices
  • 3:
    Connecting them in parallel increases the total value
  • 4:
    Oppose sudden changes in voltage
8:

The power factor of a D.C. circuit is always


Correct
  • 1:
    Less than unity
  • 2:
    Unity
  • 3:
    Greater than unity
  • 4:
    Zero
9:

The form factor is the ratio of


Correct
  • 1:
    Peak value to r.m.s. value
  • 2:
    r.m.s. value to average value
  • 3:
    Average value to r.m.s. value
  • 4:
    None of the above
10:

Pure inductive circuit takes power from the A.C. line when


Correct
  • 1:
    Applied voltage decreases but current increases
  • 2:
    Applied voltage increases but current decreases
  • 3:
    Both applied voltage and current increase
  • 4:
    Both applied voltage and current decrease
11:

The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is


Correct
  • 1:
    4 kVAR
  • 2:
    6 kVAR
  • 3:
    8 kVAR
  • 4:
    16 kVAR
12:

In a sine wave the slope is constant


Correct
  • 1:
    Between 0° and 90°
  • 2:
    Between 90° and 180°
  • 3:
    Between 180° and 270°
  • 4:
    No where
13:

The r.m.s. value of pure cosine function is


Correct
  • 1:
    0.5 of peak value
  • 2:
    0.707 of peak value
  • 3:
    Same as peak value
  • 4:
    Zero
14:

In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will


Correct
  • 1:
    Be reduced by half
  • 2:
    Be doubled
  • 3:
    Be four times at high
  • 4:
    Be reduced to one fourth
15:

Capacitors for power factor correction are rated in


Correct
  • 1:
    kW
  • 2:
    kVA
  • 3:
    kV
  • 4:
    kVAR
16:

The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of ________ degrees.


Correct
  • 1:
    90
  • 2:
    60
  • 3:
    45
  • 4:
    30

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A level AC Theory Quiz 1
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