SUMMARY for LECTURE 1
1. Electrical current is consist of the flow of electrons and flow of holes but in opposite
directions.
2. Ohm’s law V=IR
3. The power absorbed by an element is p=vi, If the
current arrow is directed into the “ +” marked terminal
an element, then p = vi yields the absorbed power. A
negative value indicates that power is actually being
generated by the element under the passive sign
convention.
of
4. Kirchhoff’s Voltage Law - The algebraic sum of the voltages equals zero for any
closed path (loop) in an electrical circuit. In a closed path, each element is
encountered only once.  Vi  0
5. Kirchhoff’s Current Law –The net current entering a node is zero  I i  0 .
Alternatively, the sum of the currents entering a node equals the sum of the currents
leaving a node.
6. A voltage divider, for a string of N series resistors, we may write:
7. A current divider, for a parallel combination of N resistors, the current through Rk is
ik 
1
Rk
1
1
1
1

 ...
R1 R2 R3 Rk
i
8. For a voltage source of current source with a fixed value of internal resistance RS , maximum
power transfer occurs when the loading RL equals to RS.