16-02-2013, 11:06 AM
Circuit Theory Laws
Circuit Theory.ppt (Size: 1.96 MB / Downloads: 679)
Circuit Theory
This presentation will
Define voltage, current, and resistance.
Define and apply Ohm’s Law.
Introduce series circuits.
Current in a series circuit
Resistance in a series circuit
Voltage in a series circuit
Define and apply Kirchhoff’s Voltage Law.
Introduce parallel circuits.
Current in a parallel circuit
Resistance in a parallel circuit
Voltage in a parallel circuit
Define and apply Kirchhoff’s Current Law.
Electricity – The Basics
An understanding of the basics of electricity requires the understanding of three fundamental concepts.
Voltage
Current
Resistance
A direct mathematical relationship exists between voltage, resistance, and current in all electronic circuits.
Voltage, Current, & Resistance
Current – Current is the flow of electrical charge through an electronic circuit. The direction of a current is opposite to the direction of electron flow. Current is measured in AMPERES (AMPS).
Current
Current – Current is the flow of electrical charge through an electronic circuit. The direction of a current is opposite to the direction of electron flow. Current is measured in AMPERES (AMPS).
Current Flow
Conventional Current assumes that current flows out of the positive side of the battery, through the circuit, and back to the negative side of the battery. This was the convention established when electricity was first discovered, but it is incorrect!
Electron Flow is what actually happens. The electrons flow out of the negative side of the battery, through the circuit, and back to the positive side of the battery.
Engineering vs. Science
The direction that the current flows does not affect what the current is doing; thus, it doesn’t make any difference which convention is used as long as you are consistent.
Both Conventional Current and Electron Flow are used. In general, the science disciplines use Electron Flow, whereas the engineering disciplines use Conventional Current.
Since this is an engineering course, we will use Conventional Current .
Summary of Kirchhoff’s Laws
Kirchhoff’s Voltage Law (KVL):
The sum of all of the voltage drops in a series circuit equals the total applied voltage.
Kirchhoff’s Current Law (KCL):
The total current in a parallel circuit equals the sum of the individual branch currents.