4B Unit 3

Effective current value is also known as the ____ value.

"Root-Mean-Square" (RMS)

Voltage induced in a wire by its own expanding and collapsing electromagnetic field is known as ____.

"self- induced voltage"

For alternating current, the effective value can be determined by using which of the following formulas?

-Effective Value = RMS Value -Effective Value = Peak Value x 0.707 -Effective Value = Peak Value/1.414

The voltage produced by an ac generator is dependent upon the _____.

-number of turns of wire -strength of the magnetic field -speed of rotation of the coil

What's the power factor for a ballast rated 0.50A at 277V supplying a 2 × 4 fixture containing four 32W bulbs?

0.92

A three-phase generator has each of its three windings evenly spaced around the rotor and the windings are ____ out-of-phase from each other.

120°

What's the current flow in amperes through a 1,800W load rated 120V when connected to a 120V power source?

15 A

What size kVA rated transformer is required for ninety-six, 150W incandescent luminaires?

15 kVA

A self-induced voltage waveform, also known as counter-electromotive force (CEMF), is _____out-of- phase with the applied voltage waveform.

180°

____ is the ability of a device to store electrical energy and to release that energy.

Capacitance

Capacitance is measured in units of _____.

Farads (F)

____ is a measurement of how far the current waveform is out-of-phase with the voltage waveform.

Power factor

True power is the total energy consumed and is expressed in _____.

Watts (P)

In circuits with _____loads, the voltage waveform finishes after the current waveform so the voltage "lags" the current.

capacitive

When a _____has reached its maximum potential difference between its metal plates, it's said to be "charged".

capacitor

To discharge a capacitor, a _____path is required between its positive (+) and negative (-).

conductive

A waveform is a mathematical representation on a graph that can be used to visualize the level and direction of _____in a circuit.

current or voltage

Frequency is expressed as ____ or \"Hertz\" (Hz).

cycles per second

For current to flow through a circuit, the power source must apply enough ____ to cause electrons to flow.

electromotive force (voltage)

The most significant use of self-induction for industry includes _____.

generators, transformers, and motors

In circuits with _____loads, the voltage waveform finishes its cycle before the current waveform, so the voltage waveform "leads" the current waveform.

inductive

The electromagnetic field intensity of a coil of wires (winding) carrying alternating current can be increased by inserting a soft _____core within the wire winding.

iron

A nonsinusoidal (or nonsymmetrical) waveform is produced when multiple alternating-current waveforms of different frequencies are introduced on a circuit, typically by _____.

nonlinear loads

Capacitors are often used to ____ pulsating direct-current waveforms when ac is rectified to dc.

smooth out

The total power consumed in a parallel circuit equals the ____ of the powers in each branch.

sum

When a wire is coiled into adjacent loops (helically wound), it's called a(an) _____.

winding