Voltage and Current Sources Resistors Ohms Law Chapter 2-1 Voltage and Current Sources Resistors Ohms Law

Current and Voltage Sources Ideal Voltage Source: Maintains a fixed voltage at its terminals regardless of the current flowing through it Ideal Current Source: Maintains a fixed current through its terminals regardless of the voltage at the terminals

Two types of ideal Sources Independent Source: provides voltage or current in the circuit that does not depend on other voltages or currents in the circuit Dependent Source (controlled source): provides voltage or current in the circuit whose vales depend on other voltages or currents in the circuit

Independent Sources

Dependent Sources

Which are Valid

Compute

1. Is it valid? 2. Which sources are delivering and absorbing power

What is alpha makes it valid

Resistance Electrical Resistance: is the measure of a materials ability to impede the flow of electrical charge Resistor (R): is the circuit element that provide resistance, unit of measure is in ohms Conductance (G): is the reciprocal of resistance, measured in Siemens.

The first two bands indicate numeric values. Four band Resistor The first two bands indicate numeric values. The third band is the multiplier. The fourth band is the tolerance. Example: [Red2][Green5][Yellow10k][Silver10%] Resistor value = 25 x 10k = 250 kOhm 10% Five band Resistor (High precision) The first three bands are numerical values. The fourth band is the multiplier. The fifth band is the tolerance. [Blue6][Gray8][Red2][Blue1M][Brown1%] Resistor value = 682 x 1M = 682 MOhm 1%

Type Characteristics Carbon Least expensive, wide available range of values and tolerances, typically used for low power and low frequency applications Metal Film Used in higher voltage applications and where high precision is called for. These devices exhibit internal capacitance, due to the metal film deposits, which can cause changes in the device impedance at higher frequencies. Wirewound Used for medium to high voltage applications requiring high power handling. However due to their geometry they exhibit high inductive properties, making them suitable only for lower frequency applications.

Ohms Law Ohm’s Law Ohm’s Law gives a relationship between a material’s resistance, R, the voltage across it, v, and the current flowing through it, i.

Find missing values and power dissipated in resistors

Find missing values and power dissipated in resistors

Find missing values and power dissipated in resistors

Now we have and expression for ohms law and power Note: Resistors can only dissipate power in the circuit, not create -- the resistor is an example of a passive circuit element --

Voltage and Current Sources Resistance. Conductance, and Resistors What you should know Voltage and Current Sources Resistance. Conductance, and Resistors Ohms law and applications Watch Me