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Electricity 101

Circuits

The route electrons can flow along. There is closed circuit (current can flow) and open circuit.

Voltage

Describes the “pressure” that pushes electricity. The amount of voltage is indicated by a unit known as the volt (V), and higher voltages cause more electricity to flow to an electronic device. Electronic devices are designed to operate at specific voltages; excessive voltage can damage their circuitry. alt text

Current

Current is the flow of electrons, measured in Amperes (Amps) past a single point in a citcuit within a set amount of time. A current of 1 ampere means that 1 coulomb of electrons—that’s 6.24 billion billion (6.24 x 1018) electrons—is moving past a single point in a circuit in 1 second.

Symbols used for amps:

  • A = amperes, for a large amount of current (1.000).
  • mA = milliamperes, a thousandth of an amp (0.001).
  • µA = microamperes, a millionth of an amp (0.000001).
Alternating Current
  • Current moves back and forth with the changing of magnetic field.
  • Represented by the symbols Alternating current symbol alt text or Alternating current symbol alt text on a digital multimeter.
  • Flows in a sine wave pattern (shown below); reverses direction at regular intervals.
  • Common source: household electrical receptacles powered by a public utility.
Direct Current

Direct current (dc):

  • Represented by the symbols Direct current symbol alt text or Direct current symbol alt text on a digital multimeter.
  • Flows only in one direction.
  • Common source: batteries or dc generator.

Resistance

Restriction to the flow of electrons - this helps protect components. Resistance is measured in Ohms (Ω)

Ohm’s Law

Electricity flows as a current. You can imagine it as a flow of water, like in a river. The water in rivers flows from mountains upstream to the ocean downstream. In other words, water flows from places with a high water height to places with a low water height. Electricity acts similarly: the concept of water height is analogous to electric potential, and electricity flows from places with high electric potential to places with low electric potential.

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The potential difference between two places can be expressed as a voltage. Voltage is the “pressure,” as it were, that makes electricity flow. In physics, voltage can be calculated using Ohm’s Law, which tells us that voltage equals resistance times current (V = IR).

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Inductor

Current passing through a coil causes a magnetic field

Electromagnetic Induction

Passing a magnetic field through a coil will induce a voltage and current

Capacitors

Store electric energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other.

Symbols Cheat Sheet

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