Basic Electricity 2
what is discontinuity?
it indicates that a circuit is broken or not continuous
In a circuit containing only inductance, the current reaches maximum value, _____ than the voltage
later
The pulse structure polarity is composed of what two edges?
leading and trailing
Positive pulse transition is from what state to what state?
lower state to higher state
What uses electro magnetism to amplify a signal?
magnetic amplifiers
what is a frequency?
number of cycles of alternating current per speed (1 second)
What are the 4 physical parameters that affect inductance
number of turns cross-sectional area length of a coil core material around which the coil is formed
What factors does the value of an emf depend on?
number of wires moving through a magnetic field strength of magnetic field speed of rotation
The unit for the measurement of impedance is what?
ohm
What are current transformers used for?
used in AC power supply systems to sense generator line current and to provide a current
What are the two classes of transformers?
voltage transformer and current transformer
When is feedback positive?
when the signal being returned to the input is in phase with the input signal
When is feedback negative?
when the signal being returned to the input is out of phase with the input signal
When two waves are in step with each other, it is said that they are what?
In phase
What takes place in AC circuits that does not take place in DC circuits?
Inductive reactance Capacitive reactance
What is the common mode of failure in an inductor?
an open
What is a transformer?
A transformer changes electrical energy of a given voltage into electrical energy at a different voltage level
Why has AC replaced some DC systems in commercial power systems?
It can be transmitted over long distances more readily and more economically
What is a power transformer?
It is used to step up or step down voltages and current in many types of power supplies
What is feedback?
Occurs when a small portion of the output signal is sent back to the input signal to the amplifier
When two waves forms go through their maximum and minimum points at different times, they are considered what?
Out of phase
what is short circuit?
an unintentional low resistance path between two components in a circuit or between a component/conductor and ground. It usually creates high current flow, which will burn out or cause damage to the circuit conductor or components
How is true power obtained?
by a wattmeter
How are inductors classified?
by the type of core and the method of winding them
What is Eddy current loss?
caused by electric currents induced in the transformer core by the varying magnetic fields
what is a wavelength?
distance that a waveform travels during a period
What is a fixed capacitor?
have approximately constant capacitance
What is the basic unit of inductance?
henry
What is the standard unit of measurement for frequency?
hertz
Negative pulse transition is from what state to what state
higher state to lower state
When using a multimeter, you test capacitors in what?
ohms
What is trouble shooting?
the systematic process of recognizing the symptoms of a problem
What determines the type of voltage transformer as being a step up type or a step down type?
the turns ratio
What is the basic function of all amplifiers?
Gain
The total opposition is called what?
Impedance
When a wave form is leading or lagging, 360 degrees is said to be ____ ____ while 180 degrees is considered ______ ___ _____
In Phase Out of phase
What are some advantages of magnetic amplifiers?
Very high efficiency High reliability Very rugged No warm-up time
What letter represents Impedance?
Z
What is an open circuit?
a circuit that is not a complete or continuous path.
What is an amplifier?
a device that enables an input signal to control an output signal
Power gain (watts) is used to describe the operation of what?
a large signal amplifier
What is inductive reactance?
a measure of how much the countering emf in the circuit will oppose current variations
In a circuit containing only capacitance, the current reaches is maximum value _____ of the voltage
ahead
With magnetic amplifiers, what does frequency range to?
100 hertz or less
What is a microprocessor?
A device that can be programmed to perform arithmetic and logical operations and other functions in a preordered sequence
In a AC parallel, they are basically the same as in AC series, but what do you do instead?
Addition
The combined effects of what three things make up the total opposition to current flow in AC circuit?
Resistance Inductive Reactance Capacitive Reactance
In a AC series, the circuits containing resistance with both inductive and capacitive reactance is combined by what?
Subtraction
What is Hysteresis loss?
The electrical energy required to magnetize the transformer core, first in one direction and then in the other
What is Faraday's Law?
The induced emf or electromagnetic force in a closed loop of wire is proportional to the rate of change of the magnetic flux through a coil of wire
What is true power?
The power dissipated in the resistance of a circuit, or the power actually used in a circuit
What are the two types of feedback?
positive and negative
Logic circuits are usually divided into two broad classes known as what?
positive and negative polarity
What is a cycle?
repetition of a pattern
In an electrical circuit, a capacitor serves as a ______ or ____ for electricity
reservoir storehouse
The decrease in alternating current frequency increases the capacitive reactance. The point that these two meet is called the what?
resonant frequency
The simple generator constitutes one method of generating voltage. It consist of a _____ ____ placed between two ______ _____.
rotating loop magnetic poles
Voltage gain describes the operation of a what?
small gain amplifier
The product of the effective voltage and the effective current is called what?
the apparent power
The basic arrangement and circuit design in microprocessors is known as what?
the architecture
What is self inductance?
the generation of a voltage in an electric circuit by a changing current in the same circuit
The ratio of a true power to the apparent power is called what?
the power factor
what is the turns ratio?
the ratio of the number of turns in the primary winding to the number of turns in the secondary winding
what is continuity?
the state of being continuous, uninterrupted, or connected together
What is a period?
time required for a sine wave to complete one full cycle
What is the difference between AC and DC ?
DC current flow in only one direction and AC current changes direction at regular intervals
The power apparently available for use in an AC circuit containing a reactive component is called what?
Apparent power
What are some disadvantages of magnetic amplifiers?
Cant handle low voltage signals Not usable in high-frequency applications Time delay associated with magnetic affects Poor fidelity
What is constructed of 2 parallel plates separated by a nonconductor, called a ______ (two answers)
Capacitor dielectric
What is the basic unit of capacitance?
Coulombs/ the letter is Q
