T5B: Concepts, units and calculation of resistance, inductance and capacitance values in series and parallel circuits

The ohm is the basic unit of resistance. Resistance in an electric circuit opposes the flow of electrons.

One ohm is defined as the resistance of a circuit in which a 1-amp current flows when 1 volt is applied.

One reason resistors are used in electronic circuits is to control the amount of current that flows for a particular applied voltage.


The ability to store energy in a magnetic field called inductance.

One reason inductors are used in electronic circuits is to reduce the flow of AC while allowing DC to pass freely.


The ability to store energy in an electric field called capacitance.

One reason capacitors are used in electronic circuits is to block the flow of direct current while allowing alternating current to pass.


If two resistors are connected in series, their total resistance is the sum of the individual resistor values.

If two equal-value inductors are connected in parallel, their total inductance is half the value of one inductor.

If two equal-value capacitors are connected in series, their total capacitance is half the value of either capacitor.