Question 1

The greatest rate of current change occurs when the current passes from negative through zero and begins to increase in the positive direction.

Accepted Answer

This is due to the fact that the slope of the sinusoidal waveform is steepest at the zero crossing point.

Question 2

Inductive reactance is proportional to ____.

Accepted Answer

Inductive reactance is proportional to the number of turns of wire in an inductor. The greater the number of turns, the higher the inductance and therefore the higher the reactance.

Question 3

Resistive loads produce heat.

Accepted Answer

Resistive loads, like incandescent bulbs, heaters, and stovetops, work by converting electrical energy into heat. Therefore, they produce heat.

Question 4

Inductance (____) is one of the primary types of loads in alternating current circuits.

Accepted Answer

Inductance is commonly represented by the symbol L in electrical circuits.

Question 5

VARs is an abbreviation for ____.

Accepted Answer

The answer of VARs is an abbreviation for ____.
...

Question 6

An induced voltage ____ the applied voltage.

Accepted Answer

According to Faraday's law of electromagnetic induction, the induced voltage is always opposite in polarity to the applied voltage.

Question 7

In a pure inductive circuit the current ____.

Accepted Answer

In a pure inductive circuit, the current lags the voltage by 90 degrees. This is due to the fact that in an inductor, the voltage leads the current by 90 degrees. Thus, when the voltage across the inductor reaches its maximum, the current is still at zero. As the voltage decreases, the current starts to increase, and when the voltage reaches zero, the current reaches its maximum. As the voltage becomes negative, the current starts to decrease, and when the voltage reaches its negative peak, the current is back to zero. Therefore, the current lags the voltage by 90 degrees in a pure inductive circuit.

Question 8

An inductor has an inductance of 0.8 H and is connected to a 120-V, 60-Hz line. How much current will flow in this circuit if the wire resistance of the inductor is negligible?

Accepted Answer

The reactance of an inductor can be calculated using the formula Xl = 2πfL, where Xl is the inductive reactance, f is the frequency, and L is the inductance.

Plugging in the given values, we get Xl = 2π(60)(0.8) = 301.59 Ω.

Using Ohm's law, we can find the current through the circuit: I = V/Xl = 120/301.59 = 0.398 A.

Therefore, the answer is C.

Question 9

An electrical measurement called ____ is used to measure the reactive power in a pure inductive circuit.

Accepted Answer

Reactive power is measured in VARs (volt-amps reactive), which represents the difference between the real power (measured in watts) and the apparent power (measured in volt-amps or VA). In a pure inductive circuit, there is no real power being consumed, only reactive power, which is proportional to the inductance of the circuit. Therefore, VARs are the most appropriate unit of measurement for reactive power in this case. AMPs (amperes) and RMSs (root-mean-square) are used to measure electrical current and voltage, respectively, but do not directly relate to reactive power.

Question 10

Sometimes the current will rise and fall at the same rate as the voltage and will reverse the direction of flow when the voltage reverses polarity. In this condition, the current is said to be ____ with the voltage.

Accepted Answer

When the current rises and falls at the same rate as the voltage and reverses direction with the voltage, it is said to be in phase with the voltage. This indicates a resistive load.

Question 11

When magnetic lines of flux cut through a coil, a voltage is induced in the coil.

Accepted Answer

This is known as electromagnetic induction and is the basis for how generators and transformers work.

Question 12

How much voltage is necessary to push 0.8 A of current through 6 ohms of resistance?

Accepted Answer

We can calculate the voltage using Ohm's law, which states that Voltage = Current x Resistance. 
Voltage = 0.8 A x 6 ohms = 4.8 V. Therefore, the answer is C.

Question 13

In a pure inductive circuit, ____.

Accepted Answer

In a pure inductive circuit, the current lags behind the voltage by 90 degrees, which means that there is no true power or watts produced. This is because the power oscillates back and forth between the source and the inductor, resulting in a net transfer of zero energy over time.

Question 14

The amount of induced voltage is proportional to the ____.

Accepted Answer

The amount of induced voltage in a conductor is proportional to the rate of change of current through it, according to Faraday's Law of Electromagnetic Induction. This principle is fundamental in the operation of transformers, electric motors, and generators.

Question 15

The current-limiting property of the inductor is called ____ and is symbolized by the letter ____.

Accepted Answer

The current-limiting property of an inductor is its reactance, which is symbolized by the letter X. Therefore, the correct choice is D) reactance, X.

Question 16

The schematic symbol used to represent an inductor depicts a coil of wire.

Accepted Answer

The schematic symbol for an inductor is a coil of wire.

Question 17

The amount of induced voltage in an inductor can be computed if the resistance of the wire in the coil and ____ are known.

Accepted Answer

The induced voltage in an inductor is directly proportional to the rate of change of current through the coil. This change in current is determined by the circuit current flowing through the inductor and the resistance of the wire in the coil. Therefore, if the resistance and circuit current are known, the induced voltage can be calculated using Faraday's law of electromagnetic induction. The other options, such as length of the circuit, any alternating current sources, and its capacitance do not directly affect the induced voltage in an inductor.

Question 18

True power, or watts, can be produced only when ____.

Accepted Answer

True power, which is the actual power being used in a circuit, can only be produced when both the voltage and current are either positive or negative. When the voltage and current are opposite in polarity, the power produced is called reactive power, which is not useful for doing work. When the voltage and current have different frequencies, the power produced is called apparent power, which is also not useful for doing work. Therefore, the only way to produce true power is when the voltage and current are both positive or both negative.

Question 19

A great amount of true power is produced in a pure inductive circuit.

Accepted Answer

A pure inductive circuit only stores and releases energy, but it does not dissipate any power because there is no resistance. Therefore, no true power is produced in a pure inductive circuit.

Quiz 10: Alternating Current Loads