NS2 5.3 Basic Electricity

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Bishop Kenny NJROTC Naval Science Two Basic Electricity

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NS2 5.3 Basic Electricity

  1. 1. CHAPTER 3 BASIC ELECTRICITY
  2. 2. The study of electricity began with the ancient Greeks.
  3. 3. Rubbing amber with a cloth created a force that attracted the cloth to the amber.
  4. 4. Rubbing two pieces of amber with two cloths caused the cloths to repel one another as much as they were attracted to the amber.
  5. 5. The forces the Greeks observed were called electric (from the Greek word for amber).
  6. 6. The cloths and amber were said to be electrically charged.
  7. 7. The Greeks could not explain electrical force.
  8. 8. The true cause of electricity was determined with the development of the atomic theory of matter.
  9. 9. Electricity The presence and motion of electrons, protons, and other charged particles Manifests itself as attraction, repulsion, luminous and heating effects
  10. 10. Scientists could explain electrical charges when they found atoms were composed of negatively charged particles (electrons) orbiting positively charged particles (protons) and neutrons which have no charge.
  11. 11. Under most conditions, an atom will have no charge.
  12. 12. If the number of electrons is increased, an atom becomes negatively charged.
  13. 13. If electrons are removed, an atom will have a positive charge.
  14. 14. Charged atoms are called ions.
  15. 15. Unlike charges attract each other while like charges repel each other.
  16. 16. In the atom, electrons are held in their orbit by the attractive force between them and protons in the nucleus.
  17. 17. In the Greeks' experiments with amber, the cloth picked up electrons from the amber, becoming negatively charged.
  18. 18. This left the amber with a positive charge, and unlike charges attract one another.
  19. 19. Conductors and Insulators Insulator Conductor
  20. 20. An electric charge can move through a material if it has a large number of free electrons.
  21. 21. Electrons can easily move from atom to atom in material with a large number of free electrons.
  22. 22. Substances that allow free movement of electrons due to their atomic structure are called conductors.
  23. 23. Conductor A material or object that permits an electric current to flow easily
  24. 24. Silver, copper, and aluminum wire, in that order, are the best conductors.
  25. 25. Copper and aluminum wire are the most commonly used because they are the the least expensive.
  26. 26. Electrical energy is conveyed as a wave traveling at the speed of light through conductors by free electrons.
  27. 27. As the electrical energy passes, each electron moves a short distance to the next atom, displacing one or more electrons by forcing them out of their orbits.
  28. 28. The replaced electrons repeat the process in other nearby atoms.
  29. 29. Some substances have very few free electrons and are therefore poor conductors.
  30. 30. Rubber Glass Wood These substances, such as rubber, glass, or dry wood, are called insulators.
  31. 31. Insulators Materials that are poor conductors (as in electricity or heat) Materials that have few free electrons
  32. 32. Good conductors such as wire carry electricity and are covered by insulating material to prevent electricity from being diverted from the conductors. Insulator Conductor
  33. 33. Voltage
  34. 34. The force that causes electricity to move in a conductor is called voltage (V) or electromagnetic force (E).
  35. 35. Voltage Electric potential or potential difference expressed in volts
  36. 36. Electromotive Force Something that moves or tends to move electricity; the potential difference derived from an electrical source per unit quantity of electricity passing through the source (such as a cell or generator)
  37. 37. Six Basic Ways to Generate Voltage • Friction • Pressure • Heat • Light • Chemical action • Magnetism
  38. 38. Friction Voltage can be produced by rubbing two materials together.
  39. 39. Static electricity is the most common name for electricity generated through friction.
  40. 40. Static electricity occurs frequently in dry climates or during low humidity.
  41. 41. Pressure Voltage can be produced by squeezing crystals such as natural quartz or manufactured crystals.
  42. 42. Compressed electrons tend to move through a crystal at predictable frequencies.
  43. 43. Crystals are frequently used in communications equipment.
  44. 44. Heat Voltage can be produced by heating the place where two unlike metals are joined.
  45. 45. The hot junction where the moving electrons from the metals meet is called a thermocouple.
  46. 46. Thermocouple A device for measuring temperature in which a pair of wires of dissimilar metals (such as copper and iron) are joined and the free ends of the wires are connected to an instrument (such as a voltmeter) that measures the difference in potential created at the junction of the two metals
  47. 47. The difference in temperature of the two metals determines the amount of voltage.
  48. 48. Thermocouples are often used to measure and regulate temperature, as in a thermostat.
  49. 49. Light Voltage can be produced when light strikes a photosensitive (light-sensitive) substance.
  50. 50. Light dislodges electrons from their orbits around surface atoms.
  51. 51. Voltage produced in this manner is called photoelectric.
  52. 52. Photoelectric Involving, relating to, or utilizing any of various electrical effects due to the interaction of radiation (such as light) with matter
  53. 53. The photoelectric cell is the device that operates on this principle.
  54. 54. A plate coated with compounds of silver or copper oxide, which are extremely sensitive to light, can also produce a flow of electrons.
  55. 55. Light is used to generate voltage in devices requiring extreme precision such as television cameras and burglar alarms.
  56. 56. Chemical Action Voltage can be produced by chemical reactions, as in a battery cell.
  57. 57. A simple voltaic battery consists of a carbon strip (positive) and a zinc strip (negative) suspended in a solution of water and sulfuric acid.
  58. 58. The solution is called the electrolyte.
  59. 59. The chemical action that results from this combination causes electrons to flow between the zinc and carbon electrodes.
  60. 60. Aircraft Automobile Equipment Boats Batteries are used as sources of electrical energy in automobiles, boats, aircraft, ships, and portable equipment.
  61. 61. Magnetism Voltage can be produced when a conductor moves through a magnetic field cutting the field's line of force.
  62. 62. This method is used in electrical generators and is the most common source of power.
  63. 63. Usually, a copper-wire conductor is moved back and forth through the magnetic field created by a U- or C-shaped electromagnet.
  64. 64. Voltmeter An instrument designed to measure voltage in an electrical circuit is called a voltmeter.
  65. 65. Electrical Current The movement of electrons through a conductor
  66. 66. Current A flow of electric charge; also, the rate of such flow
  67. 67. Direct Alternating Current Current There are two general types of electrical current: direct and alternating currents.
  68. 68. Direct current flows continuously in the same direction.
  69. 69. Alternating current periodically reverses direction.
  70. 70. An ampere (or amp) is the unit used to measure the rate of current flow.
  71. 71. The symbol for current flow is I.
  72. 72. Ammeter An instrument designed to measure electrical current is called an ammeter.
  73. 73. Every material offers some resistance or opposition to electric current flow.
  74. 74. Good conductor Very little resistance Insulator/poor conductor High resistance
  75. 75. The size and composition of wires in an electric circuit are designed to keep resistance as low as possible.
  76. 76. A wire's resistance depends on: • Length • Diameter • Composition • Temperature
  77. 77. Manufactured circuit elements that provide a measured amount of resistance are called resistors.
  78. 78. Resistance is measured in ohms (symbol: Ω, the Greek letter omega).
  79. 79. Ohm The resistance of a circuit element (or circuit) that permits a steady current of one ampere to flow when a constant potential difference of one volt is applied to that circuit
  80. 80. One ohm is the resistance of a circuit that permits one ampere to flow when a potential difference of one volt is applied to the circuit.
  81. 81. Resistance The opposition offered by a body or substance to the passage through it of a steady electric current
  82. 82. Ohmmeter An instrument used to measure resistance in an electrical circuit is called an ohmmeter.
  83. 83. Batteries
  84. 84. A battery consists of one or more cells assembled in a common container to act as a source of electrical power.
  85. 85. A cell is the fundamental unit of a battery.
  86. 86. A simple cell consists of two electrodes placed in a container of electrolyte.
  87. 87. Electrodes Conductors by which current leaves or returns to the electrolyte Electrodes
  88. 88. Carbon Zinc In a simple cell, electrodes are carbon and zinc strips placed in electrolyte.
  89. 89. Ammonium Chloride Paste In a dry cell battery, there is a carbon rod in the center of an ammonium chloride paste, which is encased in a zinc container. Carbon Rod Zinc Container
  90. 90. The electrolyte may be a salt, acid, or an alkaline solution.
  91. 91. In an automobile battery, the electrolyte is in liquid form.
  92. 92. In a dry cell battery, the electrolyte is a paste.
  93. 93. Copper Zinc A primary cell is one in which the chemical action eats away one of the electrodes.
  94. 94. Eventually the electrode must be replaced or the cell discarded.
  95. 95. In the case of a common dry cell (flashlight battery), it is usually cheaper to buy a new cell.
  96. 96. A secondary cell is one in which the electrodes and electrolyte are altered by a chemical action that generates current.
  97. 97. These cells can be recharged by forcing an electric current through them in a direction opposite to the current discharge.
  98. 98. A common example of a secondary cell battery is the automotive battery.
  99. 99. The Electrical Circuit
  100. 100. A pathway for electrons and current flow is created when two unequal charges are connected by a conductor.
  101. 101. Voltage Source Conductor An electric circuit is a conducting pathway consisting of the conductor and a path through the voltage source.
  102. 102. A lamp connected by wires to a dry cell's terminals forms a simple electric circuit.
  103. 103. The electron current flows from the negative (-) terminal of the battery through the lamp to the positive (+) battery terminal.
  104. 104. The electron current continues by going through the battery from the (+) terminal to the (-) terminal.
  105. 105. Closed Current will flow as long as the circuit remains closed.
  106. 106. The Electron
  107. 107. Before electrons were discovered, it was wrongly assumed that current was a flow of positive charges from positive to negative terminals in a circuit.
  108. 108. Schematic A diagram in which symbols are used for a circuit’s components, instead of pictures A structural or procedural diagram, especially of an electrical or mechanical system
  109. 109. Transformer Switch (closed) Switch (open) Symbols are used to make diagrams easier to draw and understand.
  110. 110. Schematic diagrams aid technicians who design or repair electrical and electronic equipment.
  111. 111. Ohm's Law
  112. 112. Proved a definite relationship exists among current, voltage, and resistance George Ohm
  113. 113. Ohm's Law The current in a circuit is directly proportional to the applied voltage and inversely proportional to the circuit resistance.
  114. 114. Ohm's Law
  115. 115. I = current in amperes E E = voltage in volts I R R = resistance in ohms VOLTAGE If any two of the quantities In the equation are known, The third may be easily found.
  116. 116. Ampere The unit used to measure the rate at which current flows
  117. 117. Equation A E I=R (The formula for finding current)
  118. 118. Determining current in a basic circuit Circuit 1 E R 1.5 v 1.5 Ω I=?
  119. 119. Circuit 1 contains a resistance of 1.5 ohms and a source voltage of 1.5 volts. Circuit 1 How much current E R 1.5 v 1.5 Ω flows in the circuit? I=?
  120. 120. Circuit 1 SOLUTION E I=R E R 1.5 v 1.5 Ω 1.5 I = 1.5 I = 1 ampere
  121. 121. In many circuit applications, the current is known, and either the voltage or resistance will be the unknown quantity.
  122. 122. Equation B E = IR (The formula for finding voltage)
  123. 123. Find the voltage in this basic circuit. E R =? 1.5 Ω I = 1a
  124. 124. Find the voltage in this basic circuit. 1_ E = 1.5 E R =? 1.5 Ω E = 1.5V I = 1a
  125. 125. Equation C R= E I (The formula for finding resistance)
  126. 126. Find the resistance in this basic circuit. E R= I E R 1.5v =?Ω I = 1a
  127. 127. Find the resistance in this basic circuit. 1.5 R= 1 E R 1.5v =?Ω R = 1.5 I = 1a
  128. 128. Power
  129. 129. Electrical Power (P) The rate at which work is being done (voltage making current flow)
  130. 130. Work is done whenever a force causes motion.
  131. 131. Since voltage makes current flow in a closed circuit, work is being done.
  132. 132. Electric power rate is measured by the watt - the basic unit of power.
  133. 133. Power is equal to the voltage across a circuit, multiplied by the current through the circuit.
  134. 134. Using P as the symbol for electrical power, the basic power formula is: P = IE
  135. 135. As an example, when E equals 2 volts and I equals 2 amperes, P equals 4 watts. 4P = 2E2I
  136. 136. R1 Drawing 1 R1 Drawing 2 20 Ω 20 Ω I = 2 amps I = 4 amps E R2 E R2 200 volts 30 Ω 400 volts 30 Ω R3 R3 50 Ω 50 Ω In drawing 1, the total voltage is 200 volts. In drawing 2, the amps were doubled, 2 to 4, thus resulting in the voltage being 400 volts. When voltage is doubled and resistance remains unchanged, power is doubled twice.
  137. 137. Doubling voltage causes a doubling of current that doubles both of the factors that determine power.
  138. 138. The rate of change of power, in a circuit of fixed resistance, is the square of the change in voltage.
  139. 139. The basic power formula (P = IE) may also be expressed as: P = E²/R or P = I²R
  140. 140. Q.1. Who began the study of electricity?
  141. 141. Q.1. Who began the study of electricity? A.1. Ancient Greeks
  142. 142. Q.2. What is an ion?
  143. 143. Q.2. What is an ion? A.2. A charged atom
  144. 144. Q.3. What is the force that causes electricity to move through a conductor called, and what is its symbol?
  145. 145. Q.3. What is the force that causes electricity to move through a conductor called, and what is its symbol? A.3. Voltage; E
  146. 146. Q.4. What is the most common name for the voltage produced by rubbing two materials together?
  147. 147. Q.4. What is the most common name for the voltage produced by rubbing two materials together? A.4. Static electricity
  148. 148. Q.5. Why is the voltage produced by squeezing crystals useful in communications equipment?
  149. 149. Q.5. Why is the voltage produced by squeezing crystals useful in communications equipment? A.5. Because the voltage produced will be at predictable frequencies
  150. 150. Q.6. Why are thermocouples often used to measure or regulate temperature?
  151. 151. Q.6. Why are thermocouples often used to measure or regulate temperature? A.6. Because the difference in the temperature of the metals determines the voltage
  152. 152. Q.7. What is the voltage called that is produced when light strikes a photosensitive (light sensitive) substance?
  153. 153. Q.7. What is the voltage called that is produced when light strikes a photosensitive (light sensitive) substance? A.7. Photoelectric voltage
  154. 154. Q.8. What is a common source of electrical energy in automobiles, boats, and aircraft?
  155. 155. Q.8. What is a common source of electrical energy in automobiles, boats, and aircraft? A.8. The secondary (wet) cell battery
  156. 156. Q.9. What method is used to produce electric energy in electric generators?
  157. 157. Q.9. What method is used to produce electric energy in electric generators? A.9. Magnetism
  158. 158. Q.10. What are the two types of electric current?
  159. 159. Q.10. What are the two types of electric current? A.10. Direct and alternating
  160. 160. Q.11. What is the unit called that is used to measure the rate at which current flows, and what is its symbol?
  161. 161. Q.11. What is the unit called that is used to measure the rate at which current flows, and what is its symbol? A.11. The Ampere; I
  162. 162. Q.12. Wires in an electric circuit are designed to keep what at a minimum?
  163. 163. Q.12. Wires in an electric circuit are designed to keep what at a minimum? A.12. Electrical resistance
  164. 164. Q.13. What are circuit elements called that are manufactured to provide a definite specified amount of resistance?
  165. 165. Q.13. What are circuit elements called that are manufactured to provide a definite specified amount of resistance? A.13. Resistors
  166. 166. Q.14. What is the unit of measurement of resistance, and what is its symbol?
  167. 167. Q.14. What is the unit of measurement of resistance, and what is its symbol? A.14. The Ohm; R
  168. 168. Q.15. What is the fundamental unit of a battery called?
  169. 169. Q.15. What is the fundamental unit of a battery called? A.15. A cell
  170. 170. Q.16. What is the cell called in which carbon and zinc strips are placed in a container holding an electrolyte?
  171. 171. Q.16. What is the cell called in which carbon and zinc strips are placed in a container holding an electrolyte? A.16. A simple cell
  172. 172. Q.17. What is the cell called in which a carbon rod is placed in a zinc container with an electrolyte paste?
  173. 173. Q.17. What is the cell called in which a carbon rod is placed in a zinc container with an electrolyte paste? A.17. A dry cell
  174. 174. Q.18. What is one of the more significant features of a battery composed of secondary cells, such as an automobile battery?
  175. 175. Q.18. What is one of the more significant features of a battery composed of secondary cells, such as an automobile battery? A.18. It is rechargeable.
  176. 176. Q.19. What is a conducting pathway consisting of a conductor and a path through the voltage source?
  177. 177. Q.19. What is a conducting pathway consisting of a conductor and a path through the voltage source? A.19. An electric circuit
  178. 178. Q.20. What is a schematic?
  179. 179. Q.20. What is a schematic? A.20. A diagram in which symbols are used to represent circuit components
  180. 180. Q.21. What is Ohm’s Law?
  181. 181. Q.21. What is Ohm’s Law? A.21. I = E/R (current = volts ÷ resistance)
  182. 182. Q.22. Applying Ohm's Law to a circuit, if source voltage increases and resistance stays constant, what will circuit current do?
  183. 183. Q.22. Applying Ohm's Law to a circuit, if source voltage increases and resistance stays constant, what will circuit current do? A.22. Increase
  184. 184. Q.23. Applying Ohm's Law to a circuit, if resistance increases and source voltage remains constant, what will circuit current do?
  185. 185. Q.23. Applying Ohm's Law to a circuit, if resistance increases and source voltage remains constant, what will circuit current do? A.23. Decrease
  186. 186. Q.24. Applying Ohm's Law to a circuit, if resistance increases and source voltage increases, what will circuit current do?
  187. 187. Q.24. Applying Ohm's Law to a circuit, if resistance increases and source voltage increases, what will circuit current do? A.24. You cannot tell without knowing actual values.
  188. 188. Q.25. Applying Ohm's Law to a circuit, if voltage is 10 volts and resistance is 5 ohms, what is circuit current?
  189. 189. Q.25. Applying Ohm's Law to a circuit, if voltage is 10 volts and resistance is 5 ohms, what is circuit current? A.25. I = E/R I = 10 volts ÷ 5 ohms I = 2 amps
  190. 190. Q.26. Applying Ohm's Law to a circuit, if voltage is 5 volts and resistance is 2 ohms, what is circuit current?
  191. 191. Q.26. Applying Ohm's Law to a circuit, if voltage is 5 volts and resistance is 2 ohms, what is circuit current? A.26. I = E/R I = 5 volts ÷ 2 ohms I = 2.5 amps
  192. 192. Q.27. Applying Ohm's Law to a circuit, if voltage is 15 volts and resistance is 5 ohms, what is circuit current?
  193. 193. Q.27. Applying Ohm's Law to a circuit, if voltage is 15 volts and resistance is 5 ohms, what is circuit current? A.27. I = E/R I = 15 volts ÷ 5 ohms I = 3 amps
  194. 194. Q.28. What is the unit of measurement of power?
  195. 195. Q.28. What is the unit of measurement of power? A.28. The watt
  196. 196. Q.29. What is the electrical symbol for power, and what is the formula for calculating it?
  197. 197. Q.29. What is the electrical symbol for power, and what is the formula for calculating it? A.29. P; P = IE (power = amps x volts)
  198. 198. Q.30. In a circuit with 200 volts and 20 amps, what is circuit power?
  199. 199. Q.30. In a circuit with 200 volts and 20 amps, what is circuit power? A.30. P = IE P = 20 amps x 200 volts P = 4,000 watts (or 4 kilowatts)
  200. 200. Q.31. In a circuit with 100 volts and 10 amps, what is circuit power?
  201. 201. Q.31. In a circuit with 100 volts and 10 amps, what is circuit power? A.31. P = IE P = 10 amps x 100 volts P = 1,000 watts (or 1 kilowatt)
  202. 202. Q.32. In a circuit with 60 volts and 5 amps, what is circuit power?
  203. 203. Q.32. In a circuit with 60 volts and 5 amps, what is circuit power? A.32. P = IE P = 5 amps x 60 volts P = 300 watts
  204. 204. Q.33. In a circuit with a current of 3 amps and a resistance of 20 ohms, what is circuit power?
  205. 205. Q.33. In a circuit with a current of 3 amps and a resistance of 20 ohms, what is circuit power? A.33. P = I² x R P = 3² (amps) x 20 ohms P = 9 x 20 P = 180 watts
  206. 206. Q.34. In a circuit with a current of 4 amps and a resistance of 25 ohms, what is circuit power?
  207. 207. Q.34. In a circuit with a current of 4 amps and a resistance of 25 ohms, what is circuit power? A.34. P = I² x R P = 4² (amps) x 25 ohms P = 16 x 25 P = 400 watts
  208. 208. Q.35. In a circuit with a current of 5 amps and a resistance of 30 ohms, what is circuit power?
  209. 209. Q.35. In a circuit with a current of 5 amps and a resistance of 30 ohms, what is circuit power? A.35. P = I² x R P = 5² (amps) x 30 ohms P = 25 x 30 P = 750 watts

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