Deck 22: Inductive Circuits

Question 1

The angle between the generator voltage and its current is the ______________ angle of the circuit.

Answer 1

phase

Question 2

In a series circuit, the higher value of X_L compared with R, the more ______________ the circuit.

Answer 2

inductive

Question 3

The series voltage drops V_R and V_L have individual values that are ______________ degrees out of phase.

Answer 3

90

Question 4

The ratio of reactive power in the inductance to the real power dissipated in the resistance is the ______________ of the coil.

Question 5

______________ effect results from the fact that current in the center of a wire encounters slightly more inductance because of the magnetic flux concentrated in the metal, compared with the edges.

Question 6

In order to ______________ effective resistance for small rf coils, a litz wire should be used.

Question 7

Typically, the lower the internal resistance of a coil, the ______________ its Q.

Question 8

The reciprocal of the power factor can be considered the ______________ of the capacitor.

Question 9

A ______________ is an inductance in series with an external R to prevent the ac signal voltage from developing any appreciable output across R at the frequency of the source.

Question 10

For any inductor, the induced voltage remains ______________ if the rate of current change is constant.

Question 11

For a series RL circuit, when R is equal to or 10 times greater than X_L

A) Z_T is approximately equal to zero ohms
B) Z_T is approximately equal to infinite ohms
C) Z_T is approximately equal to R
D) Z_T is approximately equal to X_L

Question 12

How much is Z_T for a 100 ? R in series with a 100 ? inductor?

A) 100 ?
B) 1000 ?
C) 1410 ?
D) 141 ?

Question 13

A parallel circuit has

A) different branch currents
B) different voltage drops
C) one common current
D) a total voltage equal to individual voltage drops

Question 14

What is the phase relationship between I_R and V_A in a parallel RL circuit?

A) I_R leads V_A by 90°
B) I_R lags V_A by 90°
C) I_R leads V_A by 180°
D) I_R is in phase with V_A

Question 15

In a series RL circuit, the voltage drops V_R and V_L are

A) 90° out of phase
B) in phase
C) 120° out of phase
D) 45° out of phase

Question 16

In a coil, the ratio of reactive power in the inductance to the real power dissipated in the resistance is the

A) coefficient of power
B) ratio of reactance
C) hysteresis ratio
D) Q of the coil

Question 17

When radio-frequency current tends to flow at the surface of a conductor at very high frequencies, with little current in the solid core at the center is referred to as

A) coax current
B) eddy current
C) rf effect
D) skin effect

Question 18

The factors that make the effective resistance of a coil more than its dc resistance do not include which of the following?

A) Skin effect
B) Eddy currents
C) Counter emf
D) Hysteresis

Question 19

Using litz wire or stranded wire made with separate strands insulated from each other and braided can reduce

A) R_e for small rf coils
B) X_L for small rf coils
C) L for small rf coils
D) Z for small rf coils

Question 20

If the internal resistance of a coil is low

A) its Q is low
B) its Q is high
C) its Q is zero
D) its Q is infinite

Question 21

The quality Q of a capacitor in terms of minimum loss is often indicated by its

A) capacitance
B) reactance
C) power factor
D) dielectric

Question 22

Inductance has the useful characteristic of providing more ohms of reactance at

A) lower frequencies
B) higher frequencies
C) resonant frequencies
D) harmonic frequencies

Question 23

An inductance in series with an external resistance used to prevent the ac signal voltage from developing any appreciable output across the resistance at the frequency of the source is called a(n)

A) coil
B) inductor
C) condenser
D) choke

Question 24

For any inductor, the induced voltage remains constant if

A) the rate of current change is varied
B) the rate of current change is constant
C) it is part of a series circuit
D) it is part of a parallel circuit

Question 25

What is the phase angle for the voltage across X_L with respect to the current through L?

A) V_L lags I_L by 90°
B) V_L leads I_L by 90°
C) V_L leads I_L by 45°
D) V_L is in phase with I_L

Question 26

In an RL circuit, as the frequency increases

A) R increases
B) R decreases
C) X_{L increases}
D) X_{L decreases}

Question 27

When sine-wave variations of current produce an induced voltage, the current

A) lags its induced voltage by 90°
B) leads its induced voltage by 90°
C) lags its induced voltage by 180°
D) lags its induced voltage by 45°

Question 28

The resultant of the phasor addition of R and X_L is

A) reactance
B) resistance
C) impedance
D) reluctance

Question 29

A trigonometric function of any angle of a right triangle, equal to the ratio of the opposite side to the adjacent side of a triangle is the

A) sine
B) cosine
C) tangent
D) cotangent

Question 30

Although X_L and R are both measured in ohms, they cannot be added by simple arithmetic.

Question 31

The phase angle for the voltage across X_L is at 180° with respect to the current through L.

Question 32

For a circuit with L and R in series, the X_L can be high for an undesired ac signal frequency, whereas R is the same for either direct current or alternating current.

Question 33

A cosine wave has its maximum values at 90° and 270° and its minimum values at 0° and 180°.

Question 34

When sine wave variations of current produce an induced voltage, the current lags its induced voltage by exactly 90°.

Question 35

Although inductive current lags inductive voltage by 90°, both waves have the same frequency.

Question 36

When a coil has series resistance, alternating current is limited by only R.

Question 37

In a series RL circuit, I and IR have a phase angle of 0°.

Question 38

When series voltage drops that are out of phase are combined, they cannot be added without taking the phase difference into account.

Question 39

Instead of combining waveforms that are out of phase, they can be added more quickly by using their equivalent phasors.

Question 40

The resultant of the phasor addition of R and X_L is their total opposition in ohms, called impedance.

Question 41

In phasor triangles for volts and ohms in a series circuit, the phasor for R, IR, or V_R is used as a reference at 0°.

Question 42

The angle between the generator voltage and its current is the phase angle of the circuit and its symbol ?.

Question 43

The tangent is a trigonometric function of any angle of a right triangle, equal to the ratio of the adjacent side to the hypotenuse of a triangle.

Question 44

In a series circuit, the higher the value of X_L compared with R, the more inductive the circuit.