A1 LT21 Flashcards
What is the difference between DC ohmic and AC effective resistance?
AC effective resistance considers other properties that oppose current flow, while DC ohmic resistance does not.
What causes heat in the iron core of a transformer?
Eddy currents
What does a wattmeter measure?
Power dissipated by a circuit
How is electric energy dissipated in an AC circuit?
Skin effect
What is an insulating material exposed to an electric field known as?
Dielectric
What is the skin effect?
Most current flows at outer surface of conductor
What happens to the dielectric in an AC circuit?
Distorted first in one direction, then in the other
Where does most of the current flow in a conductor?
Near the surface of the conductor
What causes an increase in effective resistance in a conductor?
Radiation loss
What effect does the skin effect have on the resistance of a conductor?
Increases
Why is it not possible to measure the effective resistance of an AC circuit with an ohmmeter?
Current must be flowing
What is hysteresis loss related to in an AC circuit?
Rotating magnetic domains
What happens to energy in an AC circuit with a magnetic field induced in a ferromagnetic material?
Dissipated in the form of heat.
How does increasing AC frequency affect the resistance of the iron core?
Increases it
What happens to the effective resistance of the circuit as eddy currents increase?
It increases
