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Conductors

Conductors. Conductors. These are the pathways that allow electrons to flow through an electrical circuit. Copper is excellent , silver is even better. Why don’t we use silver?. Different types of wires. Stranded Solid. Wire connectors.

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Conductors

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  1. Conductors

  2. Conductors • These are the pathways that allow electrons to flow through an electrical circuit. • Copper is excellent , silver is even better. • Why don’t we use silver?

  3. Different types of wires • Stranded • Solid

  4. Wire connectors • Some wire connectors are made to be crimped on the end of stranded conductors. After the connector is crimped on the wire, the wire can be easily secured under a termination block screw.

  5. Resistors • The resistor is used to create desirable voltage drops and limit current values in electronic circuitry. • A resistor’s wattage rating refers to the resistor’s ability to safely dissipate heat. • Resistors are grouped by ohms and watt sizes. • Fixed resistor symbol: • A potentiometer is a very common type of variable resistor.

  6. Inside a Resistor (how it works) Imagine water flowing through a pipe. If we make the pipe narrow then this will restrict the flow of water. If we force the water (current) through the narrow gap by increasing the pressure (voltage) then energy will be given off as heat. In addition, there will be a significant difference in pressure (voltage) above and below the restriction. In electronics we use a resistor when we need to reduce the voltage applied to a circuit.

  7. Resistor Color Code • Resistors commonly have 3 or 4 bands. Each band has an unique meaning. • 1st band – the value of the 1st digit of the resistance value. • 2nd band – 2nd digit of the resistance value • 3rd band – the multiplier, gives the factor of 10 that the fist 2 digits should be multiplied by. • 4th band – represents the tolerance of the resistor.

  8. Determine the following resistor’s value.

  9. Electrical Wiring • Wire gauge is a measurement of how large a wire is, either in diameter or cross sectional area. This determines the amount of electric current a wire can safely carry, as well as its electrical resistance and weight per unit of length. Wire gauge is applicable to both electrical and non-electrical wires, being important to electrical wiring and to structural cable. • It is more properly known as American wire gauge (AWG,) although it is sometimes also referred to as Brown and Sharpe (B&S) wire gauge.

  10. Mil • A circular mil is the equivalent area of a circle whose diameter is 0.001 (10-3) inch, or approximately 0.7854 millionths of a square inch. • Mils of circular wire or cable can be calculated as: • mils = 1000 d         where • d = diameter of cable or wire (inches)

  11. Example: Calculating Mil • Mils of a 1 inch wire: • mils = 1000 (1 in)     = 1000 • Mils of a 1/2 inch wire: • mils = 1000 (1/2 in) = 500

  12. The Circular Mil (CM ) • The circular mil area of a wire or cable is equal to its diameter - expressed in mils squared: • CM = mil 2 where • CM = circular mil area (CM) • The diameter in mil of a circular wire can be expressed as: • mil = CM1/2

  13. Example: Calculating Mil Area • The mil area of an 3/8 in wire (0.375 in or 375 mil) can be calculated as • CM = (375 mils) (375 mils) = 140625 cmil • The mil of an circular wire with area 140.325 CM can be calculated as • mil = 1406251/2 = 375 mils

  14. Siemens • The siemens (symbol: S) is the SI (International Systems of Units) derived unit of electric conductance and electric admittance. • One siemens is equal to the reciprocal of one ohm, and is sometimes referred to as the mho. • It is named after the German inventor and industrialist Ernst Werner von Siemens (1816-1892).

  15. Conductor Resistance • Four factors that affect conductor resistance: • Cross-section area of the conductor • Length of the conductor • Temperature of the material • Type of material used for the conductor

  16. Finding Resistance Value • What is the resistance value of 1000 feet of No. 15 copper conductor? 3.247 • What is the resistance value of 500 feet of No. 15 copper conductor? 3.247 / 2 = 1.6235 • What is the resistance value of 2000 feet of No. 15 copper conductor? 3.247 * 2 = 6.494

  17. Application • A 15-amp lighting load is connected to a 120 volt source 200 feet away. How much voltage drop or loss is caused by using a No. 14 aluminum wire? (Remember that the circuit would be 400 feet long!). Also be sure to use the aluminum wire resistance column and not the copper column. 1000x = 1632 x = 1.632 Ω V = IR V = (1.632)(15) V = 24.48 drop in volts

  18. Common Circuit Devices • Switches are installed in circuits to control the flow of electrons through the circuit. • They can be categorized by their actuator and electrical switching path. • The actuator is the mechanical device that causes the circuit to open and close. • Some of the most common actuators are the slide, toggle, rotary and push button.

  19. Single-pole Single-throw • The simplest type of switch is the single-pole single-throw switch, which is abbreviated SPST. The term single-pole means the switch provides one path for the electron flow and that it can be turned on or off. The term single-throw means that the switch controls only one circuit.

  20. Single-pole double-throw • A single-pole double-throw switch (SPDT) has one common connection point and can complete a circuit path to two different circuits. • A useful application of the single-pole double-throw switch is its ability to control a load, such as a lamp, from two different locations. • Also known as a three way switch.

  21. Other Switches • Double-pole double-throw switch (DPDT) has two common connection points and can provide two circuit paths simultaneously. • The DPDT switch is like having two SPST switches connected in parallel.

  22. Circuit Protection Devices - fuses • Common circuit protection devices are fuses and circuit breakers. • Fuses are constructed from small, fine wire. This wire is engineered to burn if certain amperages are exceeded. • Fuses are sized by their voltage and current capacity. • For example, a three amp fuse is designed to burn and open the circuit when the current exceeds three amps.

  23. Circuit breakers • A circuit breaker, sometimes called a reset, is another device used to protect a circuit from overload and short circuit conditions. • The main advantage of a circuit breaker over the fuse link is that the circuit breaker need not be replaced after tripping. • Both a fuse and a circuit breaker provides protection from overloads.

  24. Breadboards • A breadboard consists of a series of holes aligned in rows across the entire surface of an insulation material, such as plastic. Copper strips are run in parallel under the rows of holes and are used as conductor path ways. Electronic devices, such as resistors and transistors are inserted into the holes. You would most likely use a breadboard for assembling a circuit temporarily.

  25. Printed Circuit Boards • A printed circuit board (PCB) is made from a thin layer of conductor material, usually copper foil, cut in strips and attached to an insulated board. The heat sink area is a wide copper surface that is used for a common connection point for many devices, as well as to dissipate the heat generated by the electronic devices. To mass produce printed circuits the printed circuit board would be the most economical system.

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