Alternating current and Transformers

The property of inductance is present in which of following electrical circuits?

*An ac circuit *a dc circuit *a resistive circuit

Which factors determines the intersity of a magnetic field surrounding a coil?

*The amount of current flow through the coil *The type of core material *The number of turns in the conductor

Which of the following properties surronds a current-carrying conductor?

A magnetic field

before a 120-volt dc source can be used to power 12-volt load, the voltage must be reduced. Which of the following methods can be used?

A resistor placed in series with the load

Alternating current has replaced direct current in modern transmission systems because it has what advantages?

AC can be readily stepped up or down

A waveform is a graphic plot of what quantities?

Amplitude versus time

Electrostatic fields have what effect on free electrons and bound electrons?

Attracts them to the negative charges and distorts their orbits

capacitance and inductance in a circuit are similar in which of the following ways?

Both cause the storage of energy

How are inductors classified?

By core type

How are fixedd caparcitors classified?

By their dielectric materials

Which of the following factors will NOT affect the value of inductance of a coil?

Conductor tensility

What is the symbol used to denote the basic unit of measurement for inductance?

H

What is the unit of measurement for inductance?

Henry

What is the unit of measurement for inductane?

Henry

What is the unit of measurement for frequency?

Hertz

A soft iron core will increase inductance because it has whawt characteristic?

High permeability and low reluctance

Power consumed by an iron core inductor in reversing the magnetic field of the core is termed as what type of loss?

Hysteresis loss

The power consumed in a conductor in realigning the atoms which set up the magnetic field is known as what type of loss?

Hyteresis loss

The value of current of an AC waveform taken at any particular moment of time is what type of value?

Instantaneous value

Which of the following statements accurately describes the magnetic field surrounding a current-carrying conductor?

It is perpendicular to and equal along all parts of the conductor

Which of the following types of capacitors are referred to as self-healing?

Oil

Electrostatic lines of force radiate from a charged particle along what type of lines?

Straight lines

The direction of the induced voltage in an inductor may be found by application of which of the following rules?

The left-hand rule for generators

The coefficient of coupling between two coils is a measure of what factor?

The magnetic flux ratio linking the coils

Which of the following actions will increase the capacitance of a capacitor?

The plates are moved closer together

When a magnetic field moves through a stationary conductor, the electrons in orbit are affected in what manner?

They are dislodge from orbit

What type of dielectric is LEAST sensitive to power dielectric-hysteresis losses?

Vacuum

Two capacitors are indentical with the exception of the material used for the dielectric. Which of the following combinations of dielectric materials will cause the capacitors to have almost the same capacitance?

Vacuum, air

When does mutual inductance occurs between inductors?

Whenever the effect of one inductor is aided by another inductor

If the length of a coil is doubled while the number of turns is kept the same, this will have (a) what effect on inductance and (b) by what factor?

a. Decrease b. by 1/2

Two capacitors are identical with the exeption of the material used for the dielectric. Which of the following combinations of dielectric material will cause capacitor(b) to have a larger capacitance than capacitor(a)?

a. Glycerine b. Pure water

The magnetic field surrounding a straight conductor is(a)what shape, and (b) in in what position relative to the conductor?

a.Concentric circles b.Perpendicular

The maximum voltage that can be applied to a capacitor without causing current flow through the diectric is called

working voltage

One L/R time constant is equal to the time required for the current in an inductor to reach what portion of its maximum value?

63.2%

Inductors experience copper loss for what reason?

Because all inductors have resistance which dissipates power

The property of inductance offers opposition to which of the following quantities?

Changes in current

Self-induced emf is also known as what force?

Counter electromotive force

What may cause a capacitor to suffer power losses?

Dielectric hyteresis

Rapid reversals in the polarity of the line voltage applied to a capacitor will cause what type of capacitor power loss?

Dielectric-hysteresis

As the current through a capacitor increases, which of the following types of capacitor losses will increase?

Dielectric-leakage

What term applies to the power loss in an iron core inductore due to the current induced in the core?

Eddy-Current loss

The difference in potential across a resistor, created by current through the resistor is an example of which of the following forces?

Electromotive

A capacitor is a device that stores energy in a/an

Electrostatic Field

Maximum current will flow in an LR circuit after a minimum of how many time constants have elapsed?

Five

If a coild is wound in layers, its inductance will be greater than that of a similar-layer coil because of a higher

Flux linkage

If the radius of a coil is doubled, its inductance is increased by what factor?

Four

When the number of turns is increased in a coil from 2 to 4, the total inductance will increase by a factor of

Four

What is the symbol for inductance?

L

Mutual inductance between two coils is affected by which of the following factors?

Material of the windings?

Alternatin current can be defined as current that varies in

amplitude and direction

The left hand rule for generators states that the thumb of the left hand points in the direction of motion of the

conductor

When you grasp a coil in your left hand with your thumb pointing in the direction of the north pole, your fingers will be wrapped around the coil in the direction of the

current flow

What physical property is similar to inductance?

inertia

Capacitance is defined as the property of a circuit that

opposes a change in voltage

When electrons are moved in a conductor by a magnetic field, a force known by which term?

poterntial difference

Normally, most coils have cores composed of either air or

soft iron

The hollow form of nonmagnetic material found in the center of an air core coil has what purpose?

to support the windings