Question 1

The reference phasor for any a.c. circuit is normally drawn along the&#10;A) positive horizontal axis.&#10;B) positive vertical axis.&#10;C) positive vertical axis&#10;D) negative vertical axis.

Accepted Answer

The reference phasor is usually drawn along the positive horizontal axis in order to represent the voltage or current in phase with the reference axis. This convention simplifies the analysis of the circuit and the interpretation of the phasor diagram.

Question 2

The reference phasor for a parallel a.c. circuit is the __________ phasor.&#10;A) supply voltage&#10;B) current

Accepted Answer

The reference phasor for a parallel a.c. circuit is typically the supply voltage phasor because the voltage across all components in a parallel circuit remains the same, making it a common reference for analysis.

Question 3

Phasors are said to 'rotate'&#10;A) in a clockwise direction.&#10;B) in a counter-clockwise direction.

Accepted Answer

Phasors, which represent sinusoidal functions, rotate in a counter-clockwise direction in the complex plane. This indicates a positive angle or phase shift.

Question 4

Dividing an a.c. parallel circuit's phasor diagram by the reference phasor will result in&#10;A) an impedance diagram.&#10;B) an admittance diagram.&#10;C) a power diagram.

Accepted Answer

Dividing the phasor diagram of an a.c. parallel circuit by the reference phasor will result in the admittance diagram, which is a graphical representation of the admittance of each branch in the circuit. Admittance is the reciprocal of impedance, so this diagram can also be used to determine the impedance of each branch if needed. Therefore, option B is the best choice. The impedance diagram, option A, would be obtained by dividing the reference phasor by the phasor diagram, while a power diagram, option C, would require additional calculations beyond simple division of the phasor diagram.

Question 5

The reciprocal of resistance is called&#10;A) admittance.&#10;B) susceptance.&#10;C) conductance.&#10;D) conductivity.

Accepted Answer

The reciprocal of resistance is conductance, which is measured in siemens (S). Admittance is the reciprocal of impedance, susceptance is the imaginary part of reactance, and conductivity is a measure of a material's ability to conduct an electric current.

Question 6

The reciprocal of impedance is called&#10;A) admittance.&#10;B) susceptance.&#10;C) conductance.&#10;D) conductivity.

Accepted Answer

The reciprocal of impedance is admittance, which is measured in siemens (S). Admittance represents the ease with which AC current flows through a circuit.

Question 7

The SI unit of measurement for each of the above quantities is the&#10;A) ohm.&#10;B) mho.&#10;C) siemens.

Accepted Answer

The SI unit of measurement for electrical conductance is siemens. Ohm and mho are units of electrical resistance and conductance, respectively, but siemens is the preferred unit according to the International System of Units (SI).

Question 8

If a purely-resistive branch of a parallel circuit draws a current of 5 A when supplied with a voltage of 100 V, then its _________ must be __________.&#10;A) admittance, 20 mho&#10;B) susceptance, 0.05 ohm.&#10;C) conductance, 0.05 siemens&#10;D) conductivity, 20 siemens.

Accepted Answer

According to Ohm's Law, the conductance (G) of a purely resistive element is equal to the current (I) divided by the voltage (V), or G = I/V. In this case, G = 5 A / 100 V = 0.05 S (siemens), which is the same as choice C. Choices A, B, and D are incorrect because they relate to other electrical properties (admittance, susceptance, conductivity) that are not relevant for a purely resistive element.

Question 9

The admittance of a parallel a.c. circuit is the __________ its conductance and susceptance.&#10;A) difference between&#10;B) algebraic sum of&#10;C) vector sum of&#10;D) vector difference between

Accepted Answer

Admittance is a vector quantity and is given by the vector sum of conductance and susceptance.

Question 10

The phase angle of a parallel R-L circuit is the angle whose cosine is the ratio of&#10;A) resistance to impedance.&#10;B) impedance to resistance.&#10;C) resistance to reactance.&#10;D) reactance to resistance.

Accepted Answer

The answer of The phase angle of a parallel R-L...

Question 11

The phase angle of a parallel R-L circuit is also equal to the angle whose cosine is the ratio of&#10;A) conductance to admittance.&#10;B) admittance to conductance.&#10;C) conductance to susceptance.&#10;D) susceptance to conductance.

Accepted Answer

The answer of The phase angle of a parallel R-L...

Question 12

Multiplying an a.c. parallel circuit's phasor diagram by its reference phasor will result in&#10;A) an impedance diagram.&#10;B) an admittance diagram.&#10;C) a power diagram.

Accepted Answer

The answer of Multiplying an a.c. parallel circuit's phasor diagram...

Question 13

The phase angle of a parallel a.c. circuit is the angle by which the ________ __________ the __________.&#10;A) supply voltage, leads or lags, load current&#10;B) load current, leads or lags, supply voltage.

Accepted Answer

The answer of The phase angle of a parallel a.c....

Question 14

The power factor of a parallel a.c. circuit is the ratio of&#10;A) resistance to impedance.&#10;B) conductance to admittance.&#10;C) true power to apparent power.&#10;D) each of the above.

Accepted Answer

The answer of The power factor of a parallel a.c....

Deck 20: Parallel Alternating-Current Circuits