Theory Flashcards
The current flowing in an ac circuit is affected by what three circuit properties?
Resistance
Inductance
Capacitance
What makes up iron losses in an ac circuit?
Eddy currents - circulating currents built up in core due to changing magnetic field… Reduced with laminations
Hysteresis - energy lost due to magnetic friction in the core. Silicon steel in the core reduces hysteresis losses.
List three factors that affect the amount the voltage produced by a generator.
Flux density
Length of conductor
Speed ( angle)
Describe skin effect
It reduces the effective area of a conductor.
Molecular friction losses in a material due to the changing magnetic polarities is known as?
Hysteresis
This is energy loss due to the distortion of electrons inside the insulation.
Dielectric losses
What is impedence
The total opposition to current in an ac circuit
What is capacitance?
The opposition to a change in voltage
What is inductance?
The opposition to a change in current
What is resistance
The opposition to current flow on a molecular level.
What is the symbol for impedence and what is it measured in?
The symbol is Z and it is measured in ohms
What is the symbol for capacitance and what is it measured in?
Xc and measured in ohms
What is a capacitor?
2 conductive poles sandwiching a dielectric material
The affect capacitance has on an ac circuit is known as
Capacitive reactance
The affect inductance has on an ac circuit is known as.
Inductive reactance
What is inductance?
What is its symbol and unit of measurement?
Inductance is opposition to a change in current.
The symbol is ( L )
It is measured in henries (H)
Factors that affect inductance
# of turns Permeability of core Area of core Length of the core L = N^2pA/ length
What is lenzs law
A changing magnetic field in a coil will induce a voltage (counter emf) that will cause a current to flow that opposes the current that created it.
What are factors that affect counter emf?
Amount of inductance in a coil
The rate at which the current changes
Emf = change in current X Inductance
Change in time
What Is faradays law?
The amount of induced emf is directly proportional to the rate at which the lines of force are cut.
What is induction?
Move a wire through a magnetic field and a voltage will be induced across it.
Describe an inductor
Insulated Wire wound around a core.
What are two types of induction?
Mutual induction
Self-induction
What is mutual induction?
The generation of an emf in one conductor or circuit by a change of flux around a separate conductor or circuit.
