Basic Electric Theory Flashcards
What is current?
The movement of charge with a material. Defined as the passage of charge across a plane per unit time. Charge is the basic property of matter which can have positive, negative or neutral. Two objects with a like charge experience a repulsive force, opposite charge will experience an attractive force. The basic unit of charge is the coulomb. A simple analogy is that of water flowing through a pipe.
What are conductors?
Materials which permit movement of charge.
What are insulators?
Materials which don’t permit movement of charge.
What is voltage?
Defined as the difference in electric potential between two points. Can be used to define an energy source. A simple analogy likens voltage to the pressure of the water in a pipe.
Differences between AC and DC
Electricity can be supplied in one of two forms DC (Direct Current) where the current flows in one direction round a circuit from the source to the load. Typical sources that supply DC are batteries, photovoltaics, fuel cells.
AC (Alternating Current) where the current still flows from source to load but periodically changes direction typically in a sinusoidal fluctuation. The voltage also varies and changes direction.
What is a resistor?
Energy dissipated as heat, as current passes through the resistor. Resistors do not store energy. Z = R
What is an inductor?
An inductor is a reactive element. The voltage is proportional to the rate of change of current. Current lags the voltage by 90 degrees. Energy is stored and then released, energy is not dissipated. Z = j Xl
What is a capacitor?
A capacitor is another reactive element. The current is proportional to the rate of change of voltage. Current leads the voltage by 90 degrees. Energy is stored and then released, energy is not dissipated. Z = -j Xc
What is impedance?
Combinations of resistance, inductance and capacitance. Can be a combination of resistance and reactance.
