Electrical Principles Chapter 2 Energy, Voltage, Voltage Types, AC/DC, Current, Power, Restrictive Circuits, Inductive Circuits, Resistance, Heat, and Light

Energy

Energy Energy – Is the capacity to do work. There are two types of Energy – Potential and Kinetic. Potential Energy – Stored Energy. Example: Battery. Kinetic Energy – Energy in motion. Kinetic Energy is released Potential Energy. Example: Battery operated electric motor.

Energy Consumed Energy : Sources of Energy that once used can not be replaced. Example: Coal, Oil, Fossil Fuels. Renewable Energy : Solar, Wind, Water, Thermal Sources, Wood.

Voltage

Voltage Voltage: Is the amount of electrical pressure in a circuit. Voltage is measured in Volts (V). Voltage is also known as ElectroMotive Force (EMF) or Potential Difference. Pressure

Voltage Voltage is produced any time there is an excess of electrons at one terminal of a Voltage source and a deficiency of electrons at the other terminal. Voltage may be produced by electromagnetism (generators), chemicals (batteries), light (photocells or solar cells), heat (thermocouples – Nuclear power), pressure (pizioelectricity – electronic drum pads), or friction (static electricity).

Voltage Amount of Voltage in a circuit depends on the application. Example: IPODs require one or two batteries. Two types of Voltage – Alternating Current (AC) and Direct Current (DC). Alternating Current (AC) – Voltage that reverses its direction of flow at regular intervals (Two steps forward – One step back). Most common type of voltage.

Voltage Direct Current (DC) – Flows in one direction depending upon Polarity of circuit. All points in a DC circuit has Polarity. Polarity – Is the positive (+) or negative (-) state of an object. Rectifier : AC current can be changed to DC current by passing the AC current through a Rectifier. Example: Power Chargers for Cell Phones are AC/DC Rectifiers.

Current

Current Current (I) flows through a circuit when a source of power is connected to a device that uses electricity. Current (I) is the amount of electrons flowing through an electrical circuit. Current (I) is measured in Amperes (A). Current

Current An Ampere is the number of electrons passing a given point in one second. The more power a load requires, the larger the amount of Current flow. Current may be direct (DC) or alternating (AC). Two types of Current Flow – Conventional Current Flow and Electron Current Flow.

Current Conventional Current Flow is current flow from the positive (+) to negative (-). Electron Current Flow is current flow from the negative (-) to positive (+).

Power

Power Power (P) is the rate of doing work or using energy. Power may be expressed as True Power (PT ) or Apparent Power (PA). True Power (PT ) is the actual power used in an electrical circuit. Apparent Power (PA) is the product of the voltage and current in a circuit calculated without considering the phase shift that may be present between the voltage and the current in the circuit.

Power True Power is expressed in Watts (W). PT = W Apparent Power is expressed in Volt Amps (VA). PA=VA. PT is always less than PA in any circuit in which there is a phase shift between voltage and current.

Power Phase Shift is the state when voltage and current in a circuit do not reach their maximum amplitude and zero level at the same time.

Power Restrictive Circuit is a circuit that contains only resistance. In-phase is the state when voltage and current reach their maximum amplitude and zero level at the same time.

Power Inductance is the property of an electric device that opposes a change in current due to its inability to store energy in a magnetic field. Inductive Circuit is a circuit in which current lags voltage. Capacitance is the ability to store energy in the form of an electrical charge.

Power Capacitive Circuit is a circuit in which current leads voltage. The greater the Capacitance in a circuit, the larger the phase shift. Power Factor is the ratio of true power used in an AC circuit to apparent power delivered to the circuit.

Power Resistance (R) is the opposition to current flow. Resistance is measured in Ohms (Ώ). Resistance limits the flow of current in an electrical circuit. Conductors are made of materials that have very little resistance and permits electrons to move through it easily.

Power Insulators are made of a material that has a very high resistance and resists the flow of electrons. Heat is thermal energy. Electrical energy may be converted to heat. British Thermal Units (BTU) or Calories are used to measure heat.

Power One BTU is the amount of heat required to raise the temperature of 1 lb of water 1 degree Fahrenheit. One Calorie is the amount of heat required to raise 1gram of water 1 degree celcius.

Power Thermal Conductivity is the property of a material to conduct heat in the form of thermal energy. Heat Sink is a device that conducts and dissipates heat away from a component. HEAT kills electronics. Light is that portion of the electromagnetic spectrum which produces radian energy. Lumen (lm) is the unit used to measure the total amount of light produced by a light source.

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