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