EE281 - Electric Circuits

Resistive Circuits

Resistivity - Ohm's Law

The resistance of a material can be calculated as:

where \(\rho\) is the resistivity of the material, \(\ell\) is the length, \(A\) is the area. Remember to use SI units (m and m2) to get correect values.

Voltage across a resistor is proportional to current it is carrying.

A short circuit is the case where the resistance between terminals is zero.

An open circuit is the case where the resistance between terminals is infinity.

Series Resistors

The equivalent resistance of any number of resistors connected in series is the sum of the individual resistances.

Parallel Resitors

The equivalent resistance of two parallel resistors is equal to the product of their resistances divided by their sum.

Delta-Wye Transformations

Instead of two terminal equivalents, three terminal equivalents are used.

Delta Connections:

The following resistances are equal (Node C can be reduced to one point):

Wye Connections:

Transformation

Delta to Wye

Wye to Delta