BASIC LAWS

BASIC LAWSHistorical Proles

Symbol

Independent voltage sourcesIndependent current sourceDependent voltage sourceDependent current sourceOHMS LAW

ProblemAn electric iron draws 2A at 120V. Find its resistance.How much current is drawn by a toaster with resistance 12 at 110V?In the circuit shown, calculate the current i, the conductance G, and the power p.

AnswerNODES, BRANCHES, AND LOOPS

Determine the number of branches and nodes in the circuit:

Since there are four elements in the circuit, the circuit has four branches: 10 V, 5 , 6 , and 2 A. The circuit has three nodes. The 5 resistor is in series with the 10 V voltage source because the same current would ow in both. The 6 resistor is in parallel with the 2-A current source because both are connected to the same nodes 2 and 3.

KIRCHHOFFS LAWS

For the circuit, nd voltages v1 and v2.

Determine vo and i in the circuit

SERIES RESISTORS AND VOLTAGE DIVISION

PARALLEL RESISTORS AND CURRENT DIVISION

Extreme case

A shorted circuit an open circuitProblem

Three lightbulbs are connected to a 9-V battery as shown in Fig. Calculate: (a) the total current supplied by the battery, (b) the current through each bulb, (c) the resistance of each bulb.

Three lightbulbs are connected to a 9-V battery as shown in Fig. Calculate: (a) the total current supplied by the battery, (b) the current through each bulb, (c) the resistance of each bulb.