Unit 18 Flashcards
What are the three main characteristics of an Eddy current?
Flow erratically ; consume power ; and increase the opposition to current flow
Because electrons spin, they have their own what?
Magnetic fields
What happens as alternating current within a conductor increases, an expanding electromagnetic field field is created through the conductor and the magnetic flux lines cut through the conductor .
Voltage is induced within the conductor
The expanding and collapsing magnetic field from an ac circuit induces a voltage in the conductors that repels the flowing electrons towards the surface of the conductor, what is this called?
Skin effect
Induced voltage that opposes the current flow is called what?
Counter-electromotive force or CEMF
An ac circuit contains inductive reactance because the voltage and current are what with each ohter?
Not in phase
In dc circuits, the only property that affects current and voltage flow is _______
Resistance
The total opposition to current flow in an ac circuit includes what and what is it called?
Resistance and reactance ; impedance
Windings with soft iron cores produce greater self-inductance than windings with an air core because…
Iron cores provide an easy path for magnetic flux
This is the property of an electrical circuit that enables it to store electrical energy by a means of an electromagnetic field and to release this energy at a later time
Inductance
A self induced voltage waveform is ____ degrees out of phase with the applied voltage waveform
180
Will a longer core produce more or less CEMF?
Less
CEMF acts to oppose the change in current flowing in the conductor, this property is called what?
Inductive reactance
All that is required to induce voltage is a ______ and an external _____ ______ with relative motion between the two
Conductor ; Magnetic field
The movement of electrons caused by an external magnetic field is called what?
Induced current
Inductive reactance is measured in what?
Ohms
When alternating current increases, the polarity of the CEMF within the conductors _____ the conductor’s current.
Opposes
In a purely inductive circuit, the applied voltage waveform ____ the current waveform by _____ degrees
Leads ; 90
CEFM is ____ proportional to the cross-sectional area of the core and ______ proportional to its lengh
Directly ; inversely
Besides conductor resistance, alternating current flow contains an additional element called what that opposes the flow of electrons?
Reactance
When a conductor is coiled into adjacent loops (helically wound), it is called what?
A winding
Impedance is measured in what and what letter is used as the abbreviation?
Ohms ; Z
The waveform of the induced voltage in the conductor is ____ degrees out of phase with the circuit current and _____ degrees out of phase with the applied voltage waveform
90 ; 180
What are the three major uses of induction?
Transformers, motors, and generators
Conductor resistance is directly proportional to its ________ and inversely proportional to to its ______ ___
Length ; Cross-sectional area
When alternating current decreases, the polarity of the induced voltage within the conductor _____ the conductor’s current.
Aids
The amount of the self-induced voltage created within the winding is directly proportional to what three things?
Current flow, windings, and frequency
The voltage induced within the conductor caused by its own expanding and collapsing magnetic field is known as what?
Self-induced voltage
(T/F) The induced voltage in a conductor carrying alternating current sometimes opposes the change in current flowing through the conductor.
False
The associated potential that is established by induced current is called what?
Induced voltage
When electrons move, their magnetic fields combine to produce an overall magnetic field that extends _______ the conductor.
Outside
These are small independent currents that are produced as a result of the expanding and collapsing magnetic field from an ac circuit.
Eddy currents
