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Subelement A
Principles
Section 1
Electrical Elements
The product of the readings of an AC voltmeter and AC ammeter is called:
  • Correct Answer
    Apparent power.
  • True power.
  • Power factor.
  • Current power.

The product of the readings of an AC voltmeter and AC ammeter is called:

(A). Apparent power.

Multiplying volts (V) by amperes (A) produces the amount of apparent power.

When there is no impedance (resistance) in the AC circuit, then the apparent power is equal to the "true power."

So, if there is some reactance (resistance caused by inductance or capacitance or both of them) then the apparent power will be > greater than "true power."

Basically, the apparent power is what you really get. What you don't get is what is being reflected back to the source of the current.

For more info, please see Wikipedia's article on
AC Power

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What is the basic unit of electrical power?
  • Ohm.
  • Correct Answer
    Watt.
  • Volt.
  • Ampere.

What is the basic unit of electrical power?

(B).   Watt.

  • W = Volts x Amperes

When amperes flow through the difference in charges (in volts) we call it watts.

For more info, please see Wikipedia's article on Watt

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What is the term used to express the amount of electrical energy stored in an electrostatic field?
  • Correct Answer
    Joules.
  • Coulombs.
  • Watts.
  • Volts.

What is the term used to express the amount of electrical energy stored in an electrostatic field?

(A).   Joules.

Joule (J) is the amount of energy stored in a capacitor. The energy can be used to produce watts of power or move an electric charge.

For more on Joules, please see Wikipedia's article on Joule

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What device is used to store electrical energy in an electrostatic field?
  • Battery.
  • Transformer.
  • Correct Answer
    Capacitor.
  • Inductor.

What device is used to store electrical energy in an electrostatic field?

C.   Capacitor.

A capacitor is a passive circuit component that stores electrical energy in an electrostatic field.

For more info, please see Wikipedia's article on Capacitor

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What formula would determine the inductive reactance of a coil if frequency and coil inductance are known?
  • XL = πƒ L
  • Correct Answer
    XL = 2πƒ L
  • XL = 1 / 2πƒ C
  • XL = 1 / R2+X2

What formula would determine the inductive reactance of a coil if frequency and coil inductance are known?

(B).   XL = 2πƒ L

Inductive reactance opposes the flow of current in a circuit. On a graph, it is the increasing slope between reactance and frequency.

It means

  • 2(3.1416)(Frequency)(Inductance)
    or
  • 2(3.1416)(Hz)(Henry)

For excellent illustrated info, please see Electronics Tutorials site for the article on Inductive Reactance

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What is the term for the out-of-phase power associated with inductors and capacitors?
  • Effective power.
  • True power.
  • Peak envelope power.
  • Correct Answer
    Reactive power.

What is the term for the out-of-phase power associated with inductors and capacitors?

(D).   Reactive power.

In circuits, there are the active (Wats), reactive (VAR-volts/amps/reactive) and apparent powers (VA-volts/amps).

The active one is where power exerts in the circuit. The reactive one just flows between the load and the source. It cannot be used like the active power. The apparent power combines active and reactive.

For more info see:

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