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Electronic circuits and components * Course Index * Introduction * About the Author * About this Course * Feedback * Course Navigation * How to use this Course * TINA * Locktronics

Fundamentals * Introduction: Fundamentals * Units and Multiples * Electricity ## Conductors and Insulators ## Basic Circuit Symbols ##

Voltage and Current ## Resistance ## Ohm's Law ## Worksheet: Ohm's Law ## Energy and Power ## Examples: Electricity * Electronic Principles * Electrical Circuits * Alternating Current * Assessment: Fundamentals

Passive Components * Introduction: Passive Components * Resistors * Capacitors * Inductors * Transformers * Batteries, Fuses, Lamps and Switches * Assessment: Passive Components

Semiconductors * Introduction: Semiconductors * Diodes * Transistors * Logic Gates * Assessment: Semiconductors

Passive Circuits * Introduction: Passive Circuits * Series and Parallel Connections * Kirchoff's Laws * Potential and Current Dividers * Passive Time Variant Circuits * Assessment: Passive Circuits

Active Circuits * Introduction: Active Circuits * Power Supply Circuits * Operational Amplifier Circuits * Transistor Amplifier Circuits * 555 Timer Circuits * Assessment: Active Circuits

Parts Gallery * Introduction: Parts Gallery * Passive Component Images * Semiconductor Images * Other Images * Quizzes

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Voltage and Current

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Animation showing current flow in a circuit

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Animation showing electron flow in a circuit

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The ability of an energy source (e.g. a battery) to produce a current within a conductor may be expressed in terms of electromotive force (e.m.f.). Whenever an e.m.f. is applied to a circuit a potential difference (p.d.) exists. Both e.m.f. and p.d. are measured in volts (V). In many practical circuits there is only one e.m.f. present (the battery or supply) whereas a p.d. will be developed across each component present in the circuit.

The conventional flow of current in a circuit is from the point of more positive potential to the point of greatest negative potential (note that electrons move in the opposite direction!). Direct current results from the application of a direct e.m.f. (derived from batteries or d.c. supply rails). An essential characteristic of such supplies is that the applied e.m.f. does not change its polarity, even though its value might be subject to some fluctuation.

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Page last modified on July 22, 2011, at 09:04 AM