Electronics 133 chap 18,19,20

Inductive reactance is measured in

ohms

The combined reactance of parallel reactances is calculated by

the reciprocal formula

An induced voltage across a coil is actually the result of inducing electrons to move in a conductor; however there is no induced current. (t/f)

False

In a series circuit containing two inductors and a voltage source, the current is less in the inductor with the higher inductance. (t/f)

False

Inductors are not reactive components like capacitors. (t/f)

False

The base unit for inductance is

Henry

How is mutual inductance affected when primary and secondary inductances are increased and coupling is made tighter?

INCECREASE

What is the phase relationship between I R and V A in a parallel RL circuit?

IR is in phase with VA

An inductance can have X L to reduce the amount of alternating current because self-induced voltage is produced to oppose the applied voltage. (t/f)

True

One henry is the amount of inductance that allows one volt to be induced when the current changes at the rate of one ampere per second. (t/f)

True

Since reactance is an opposition in ohms, the values X L in series or parallel are combined the same way as ohms of resistance. (t/f)

True

The higher the frequency of the alternating current, and the greater the inductance, the X L opposition will be increased. (t/f)

True

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

V L leads I L by 90°

The unit of apparent power is

Volt-amps

The combined parallel inductive reactance branch will be

less than the lowest branch reactance

The ability of one coil to induce a voltage in another coil nearby is referred to as

mutual inductance

A measure that indicates the relationship between the real and apparent power values is the

power factor

The process of adding a capacitor across the AC line to offset the effects of the inductive loads is

power factor correction

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

tanget

When alternating current flows in an inductance

the current is less than the dc resistance alone would allow

The values of X L in series or in parallel are combined

the same way as ohms of resistance

The amount of current in an ac circuit with only inductive reactance is equal to the applied voltage divided by the inductance. (t/f)

False

Real power is calculated using the expression:

P = I 2R

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

Q of the coil

The unit of reactive power is the

VAR

For a series RL circuit, when R is much larger than X L

Z T is approximately equal to R

The ratio of the number of turns in the primary to the number in the secondary is the

turns ratio

What is the inductive reactance for steady direct current?

0 Ω

The ideal condition of most power circuits is a power factor of

1

Frequency is equal to

1/T

How much is Z T for a 100 Ω R in series with a 100 Ω inductor?

141 Ω

X L equals

2πfL

With an inductive circuit, the phase angle between v L and i L is

90°

Power that is assumed to be consumed by the circuit is

apparent power

The amount of power the transformer can deliver to a resistive load is called

apparent power

Which of the following is not an example of how X L is generally used?

block dc

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)

choke

The fraction of total flux from one coil linking another coil is the

coefficient of coupling

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

counter emf

An advantage of using a transformer with a separate winding secondary is

electrical isolation

For two coils with mutual inductance, any magnetic lines that do not link the two coils result in

leakage flux

Mutual inductance is also called

Mutual coupling

Inductance equals

X L/2πf

One way to express impedance is with

a complex number

The unit of mutual inductance is the

henry

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

higher frequencies

The resultant of the phasor addition of R and X L is

impedance

Inductive reactance will increase if

inductance is increased

The ratio of v L/i L specifies the

inductive reactance

If the internal resistance of a coil is low

its Q is high

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

lags its induced voltage by 90°

To minimize transformer core losses while maintaining high flux density, the core can be made of

laminated steel