The document discusses the basic principles of electricity, including how voltage is generated through various means such as friction, pressure, heat, light, chemical reactions, and magnetism. It also covers electrical components like conductors, insulators, batteries, circuits, and formulas such as Ohm's Law. The relationships between voltage, current, resistance, and power in electrical circuits are explained.

1. CHAPTER 3
BASIC ELECTRICITY

2. The study of
electricity began
with the ancient
Greeks.

3. Rubbing amber with a cloth created a
force that attracted the cloth to the
amber.

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. The forces the Greeks observed were
called electric (from the Greek word for
amber).

6. The cloths and amber were said to be
electrically charged.

7. The Greeks could
not explain electrical
force.

8. The true cause of electricity was
determined with the development
of the atomic theory of matter.

9. Electricity
The presence and motion of
electrons, protons, and other
charged particles
Manifests itself as attraction,
repulsion, luminous and heating
effects

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. Under most conditions, an atom will
have no charge.

12. If the number of electrons is increased,
an atom becomes negatively charged.

13. If electrons are removed, an atom will
have a positive charge.

14. Charged atoms are called ions.

15. Unlike charges
attract each other
while like charges
repel each other.

16. In the atom, electrons are held in their
orbit by the attractive force between
them and protons in the nucleus.

17. In the Greeks' experiments with amber,
the cloth picked up electrons from the
amber, becoming negatively charged.

18. This left the amber with a positive
charge, and unlike charges attract
one another.

19. Conductors and Insulators
Insulator Conductor

20. An electric charge can move through
a material if it has a large number of
free electrons.

21. Electrons can easily move from atom
to atom in material with a large number
of free electrons.

22. Substances that allow free movement of
electrons due to their atomic structure
are called conductors.

23. Conductor
A material or object that permits an
electric current to flow easily

24. Silver, copper, and aluminum wire, in
that order, are the best conductors.

25. Copper and aluminum wire are the most
commonly used because they are the
the least expensive.

26. Electrical energy is conveyed as a wave
traveling at the speed of light through
conductors by free electrons.

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. The replaced electrons repeat the
process in other nearby atoms.

29. Some substances have very few
free electrons and are therefore
poor conductors.

30. Rubber
Glass Wood
These substances, such as rubber,
glass, or dry wood, are called insulators.

31. Insulators
Materials that are poor conductors
(as in electricity or heat)
Materials that have few free electrons

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. Voltage

34. The force that causes electricity to
move in a conductor is called voltage (V)
or electromagnetic force (E).

35. Voltage
Electric potential or potential
difference expressed in volts

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. Six Basic Ways to Generate Voltage
• Friction
• Pressure
• Heat
• Light
• Chemical action
• Magnetism

38. Friction
Voltage can be produced by rubbing
two materials together.

39. Static electricity is the most common
name for electricity generated through
friction.

40. Static electricity occurs frequently in
dry climates or during low humidity.

41. Pressure
Voltage can be produced by squeezing
crystals such as natural quartz or
manufactured crystals.

42. Compressed electrons tend to move
through a crystal at predictable
frequencies.

43. Crystals are frequently used in
communications equipment.

44. Heat
Voltage can be produced by heating the
place where two unlike metals are joined.

45. The hot junction where the moving
electrons from the metals meet is
called a thermocouple.

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. The difference in temperature of the two
metals determines the amount of voltage.

48. Thermocouples are often used to
measure and regulate temperature,
as in a thermostat.

49. Light
Voltage can be produced when light
strikes a photosensitive (light-sensitive)
substance.

50. Light dislodges electrons from their
orbits around surface atoms.

51. Voltage produced in this manner is called
photoelectric.

52. Photoelectric
Involving, relating to, or utilizing any
of various electrical effects due to
the interaction of radiation (such as
light) with matter

53. The photoelectric cell is the device
that operates on this principle.

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. Light is used to generate voltage in
devices requiring extreme precision
such as television cameras and
burglar alarms.

56. Chemical Action
Voltage can be produced by chemical
reactions, as in a battery cell.

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. The solution is called the electrolyte.

59. The chemical action that results from
this combination causes electrons to
flow between the zinc and carbon
electrodes.

60. Aircraft
Automobile
Equipment
Boats
Batteries are used as sources of
electrical energy in automobiles, boats,
aircraft, ships, and portable equipment.

61. Magnetism
Voltage can be produced when a
conductor moves through a magnetic
field cutting the field's line of force.

62. This method is used in electrical
generators and is the most common
source of power.

63. Usually, a copper-wire conductor
is moved back and forth through
the magnetic field created by a
U- or C-shaped electromagnet.

64. Voltmeter
An instrument designed to measure
voltage in an electrical circuit is called
a voltmeter.

65. Electrical Current
The movement of electrons
through a conductor

66. Current
A flow of electric charge;
also, the rate of such flow

67. Direct Alternating
Current Current
There are two general types of electrical
current: direct and alternating currents.

68. Direct current flows continuously
in the same direction.

69. Alternating current periodically
reverses direction.

70. An ampere (or amp) is the unit used
to measure the rate of current flow.

71. The symbol for current flow is I.

72. Ammeter
An instrument designed to measure
electrical current is called an ammeter.

73. Every material offers some resistance
or opposition to electric current flow.

74. Good conductor
Very little resistance
Insulator/poor conductor
High resistance

75. The size and composition of wires in
an electric circuit are designed to
keep resistance as low as possible.

76. A wire's resistance depends on:
• Length
• Diameter
• Composition
• Temperature

77. Manufactured circuit elements that
provide a measured amount of
resistance are called resistors.

78. Resistance is measured in ohms
(symbol: Ω, the Greek letter omega).

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. 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. Resistance
The opposition offered by a body or
substance to the passage through
it of a steady electric current

82. Ohmmeter
An instrument used to measure
resistance in an electrical circuit
is called an ohmmeter.

83. Batteries

84. A battery consists of one or more cells
assembled in a common container to
act as a source of electrical power.

85. A cell is the fundamental
unit of a battery.

86. A simple cell consists of two electrodes
placed in a container of electrolyte.

87. Electrodes
Conductors by
which current
leaves or returns
to the electrolyte
Electrodes

88. Carbon Zinc
In a simple cell, electrodes are carbon
and zinc strips placed in
electrolyte.

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. The electrolyte may be a salt, acid,
or an alkaline solution.

91. In an automobile battery, the
electrolyte is in liquid form.

92. In a dry cell battery,
the electrolyte is a
paste.

93. Copper Zinc
A primary cell is one in which the
chemical action eats away one of
the electrodes.

94. Eventually the electrode must be
replaced or the cell discarded.

95. In the case of a common dry cell
(flashlight battery), it is usually
cheaper to buy a new cell.

96. A secondary cell is one in which the
electrodes and electrolyte are altered
by a chemical action that generates
current.

97. These cells can be recharged by
forcing an electric current through
them in a direction opposite to
the current discharge.

98. A common example of a
secondary cell battery is
the automotive battery.

99. The Electrical Circuit

100. A pathway for electrons and current flow
is created when two unequal charges are
connected by a conductor.

101. Voltage
Source
Conductor
An electric circuit is a conducting
pathway consisting of the conductor
and a path through the voltage source.

102. A lamp connected by wires to a dry cell's
terminals forms a simple electric circuit.

103. The electron current flows from the
negative (-) terminal of the battery
through the lamp to the positive (+)
battery terminal.

104. The electron current continues by
going through the battery from the
(+) terminal to the (-) terminal.

105. Closed
Current will flow as long as the circuit
remains closed.

106. The Electron

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. 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. Transformer
Switch (closed)
Switch (open)
Symbols are used to make diagrams
easier to draw and understand.

110. Schematic diagrams aid technicians
who design or repair electrical and
electronic equipment.

111. Ohm's Law

112. Proved a definite
relationship exists
among current,
voltage, and
resistance
George Ohm

113. Ohm's Law
The current in a circuit is directly
proportional to the applied voltage
and inversely proportional to the
circuit resistance.

114. Ohm's Law

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. Ampere
The unit used to measure the rate
at which current flows

117. Equation A
E
I=R
(The formula for finding current)

118. Determining current in a basic circuit
Circuit 1
E R
1.5 v 1.5 Ω
I=?

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. Circuit 1
SOLUTION
E
I=R
E R
1.5 v 1.5 Ω
1.5
I = 1.5
I = 1 ampere

121. In many circuit applications, the current
is known, and either the voltage or
resistance will be the unknown quantity.

122. Equation B
E = IR
(The formula for finding voltage)

123. Find the voltage in this basic circuit.
E R
=? 1.5 Ω
I = 1a

124. Find the voltage in this basic circuit.
1_
E = 1.5
E R
=? 1.5 Ω
E = 1.5V
I = 1a

125. Equation C
R= E
I
(The formula for finding resistance)

126. Find the resistance in this basic
circuit.
E
R= I
E R
1.5v =?Ω
I = 1a

127. Find the resistance in this basic
circuit.
1.5
R= 1
E R
1.5v =?Ω
R = 1.5
I = 1a

128. Power

129. Electrical Power (P)
The rate at which work is being
done (voltage making current flow)

130. Work is done
whenever a force
causes motion.

131. Since voltage makes current flow in a
closed circuit, work is being done.

132. Electric power rate
is measured by the
watt - the basic unit
of power.

133. Power is equal to the voltage across
a circuit, multiplied by the current
through the circuit.

134. Using P as the symbol for electrical
power, the basic power formula is:
P = IE

135. As an example, when E equals 2 volts
and I equals 2 amperes, P equals
4 watts.
4P = 2E2I

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. Doubling voltage causes a doubling of
current that doubles both of the factors
that determine power.

138. The rate of change of power, in a
circuit of fixed resistance, is the
square of the change in voltage.

139. The basic power formula (P = IE)
may also be expressed as:
P = E²/R
or
P = I²R

140. Q.1. Who began the study of
electricity?

141. Q.1. Who began the study of
electricity?
A.1. Ancient Greeks

142. Q.2. What is an ion?

143. Q.2. What is an ion?
A.2. A charged atom

144. Q.3. What is the force that causes
electricity to move through a
conductor called, and what is its
symbol?

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. Q.4. What is the most common name
for the voltage produced by
rubbing two materials together?

147. Q.4. What is the most common name
for the voltage produced by
rubbing two materials together?
A.4. Static electricity

148. Q.5. Why is the voltage produced by
squeezing crystals useful in
communications equipment?

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. Q.6. Why are thermocouples often
used to measure or regulate
temperature?

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. Q.7. What is the voltage called that
is produced when light strikes a
photosensitive (light sensitive)
substance?

153. Q.7. What is the voltage called that
is produced when light strikes a
photosensitive (light sensitive)
substance?
A.7. Photoelectric voltage

154. Q.8. What is a common source of
electrical energy in automobiles,
boats, and aircraft?

155. Q.8. What is a common source of
electrical energy in automobiles,
boats, and aircraft?
A.8. The secondary (wet) cell battery

156. Q.9. What method is used to
produce electric energy in
electric generators?

157. Q.9. What method is used to
produce electric energy in
electric generators?
A.9. Magnetism

158. Q.10. What are the two types of
electric current?

159. Q.10. What are the two types of
electric current?
A.10. Direct and alternating

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. 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. Q.12. Wires in an electric circuit are
designed to keep what at a
minimum?

163. Q.12. Wires in an electric circuit are
designed to keep what at a
minimum?
A.12. Electrical resistance

164. Q.13. What are circuit elements
called that are manufactured to
provide a definite specified
amount of resistance?

165. Q.13. What are circuit elements
called that are manufactured to
provide a definite specified
amount of resistance?
A.13. Resistors

166. Q.14. What is the unit of
measurement of resistance,
and what is its symbol?

167. Q.14. What is the unit of
measurement of resistance,
and what is its symbol?
A.14. The Ohm; R

168. Q.15. What is the fundamental unit
of a battery called?

169. Q.15. What is the fundamental unit
of a battery called?
A.15. A cell

170. Q.16. What is the cell called in which
carbon and zinc strips are
placed in a container holding
an electrolyte?

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. Q.17. What is the cell called in which
a carbon rod is placed in a zinc
container with an electrolyte
paste?

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. Q.18. What is one of the more
significant features of a battery
composed of secondary cells,
such as an automobile battery?

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. Q.19. What is a conducting pathway
consisting of a conductor and
a path through the voltage
source?

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. Q.20. What is a schematic?

179. Q.20. What is a schematic?
A.20. A diagram in which symbols
are used to represent circuit
components

180. Q.21. What is Ohm’s Law?

181. Q.21. What is Ohm’s Law?
A.21. I = E/R
(current = volts ÷ resistance)

182. Q.22. Applying Ohm's Law to a
circuit, if source voltage
increases and resistance stays
constant, what will circuit
current do?

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. Q.23. Applying Ohm's Law to a
circuit, if resistance increases
and source voltage remains
constant, what will circuit
current do?

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. Q.24. Applying Ohm's Law to a
circuit, if resistance increases
and source voltage increases,
what will circuit current do?

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. Q.25. Applying Ohm's Law to a
circuit, if voltage is 10 volts
and resistance is 5 ohms, what
is circuit current?

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. Q.26. Applying Ohm's Law to a
circuit, if voltage is 5 volts and
resistance is 2 ohms, what is
circuit current?

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. Q.27. Applying Ohm's Law to a
circuit, if voltage is 15 volts
and resistance is 5 ohms, what
is circuit current?

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. Q.28. What is the unit of
measurement of power?

195. Q.28. What is the unit of
measurement of power?
A.28. The watt

196. Q.29. What is the electrical symbol
for power, and what is the
formula for calculating it?

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. Q.30. In a circuit with 200 volts and
20 amps, what is circuit
power?

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. Q.31. In a circuit with 100 volts and
10 amps, what is circuit
power?

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. Q.32. In a circuit with 60 volts and
5 amps, what is circuit power?

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. Q.33. In a circuit with a current of
3 amps and a resistance of 20
ohms, what is circuit power?

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. Q.34. In a circuit with a current of
4 amps and a resistance of 25
ohms, what is circuit power?

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. Q.35. In a circuit with a current of
5 amps and a resistance of 30
ohms, what is circuit power?

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