Chapter 50 - Principles of Electrical Systems.
Tech A says that an ohm is a unit of measurement of resistance. Tech B says that high resistance creates heat at the point of resistance in the circuit. Who is correct?
Both A and B.
Tech A says that electromotive force is also known as voltage. Tech B says that when electrons flow in one direction only, this is DC. Who is correct?
Both A and B.
Tech A says that the movement of electrons in a circuit is called current flow. Tech B says that the movement of electrons in a circuit is measured in amps. Who is correct?
Both A and B.
What materials make a good insulator?
Ceramic and plastic.
__________ is achieved when an electrical circuit has a continuous and uninterrupted electrical connection and is thereby capable of conducting current and working as designed.
Continuity
Which type of current flow is produced by a battery?
Direct current.
When negative ions in a solution are attracted to the negative plate and positive ions to the positive plate, a chemical reaction can occur.
False (A chemical reaction will occur when negative ions in a solution are attracted to the positive plate and positive ions to the negative plate.)
A potential electrical difference across a crystal that will physically distort the crystal is called electromagnetic induction.
False (This is called piezoelectric energy.)
__________ __________ are only loosely held by the nucleus and are free to move from one atom to another when an electrical potential (pressure) is applied.
Free electrons
Which side of a circuit starts at the negative post of the battery and ends at either a load or a switch?
Ground side.
What of these is a by-product of the flow of electricity?
Heat.
Which of these cannot conduct electrons easily?
Insulators.
Which law states that current entering any junction is equal to the sum of the current flowing out of the junction?
Kirchhoff's current law.
All of the following are effects of the flow of electricity, except:
Mechanical action.
__________ __________ tells us that if we increase current flow through a resistance, the voltage used by that resistance will increase.
Ohm's law
How many paths are there in a series circuit?
One.
Which of the following materials is typically used in the construction of semiconductors?
Silicon.
Tech A says that a series circuit has only one path for current to flow. Tech B says that a parallel circuit current flows through one resistor before getting to the next resistor. Who is correct?
Tech A.
Tech A says that an unintended resistance results in a voltage drop. Tech B says that one of the factors that determines the level of electrical resistance is the weight of the conductor. Who is correct?
Tech A.
Tech A says that if resistance stays the same and voltage goes up, then amperage goes down. Tech B says that if voltage stays the same and resistance goes down, then amperage goes down. Who is correct?
Tech A.
Tech A says that in a series circuit with two resistors of 120 ohms each, the total circuit resistance is 240 ohms. Tech B says that in a parallel circuit with two resistors of 120 ohms each, the total circuit resistance is 240 ohms. Who is correct?
Tech A.
Tech A says that a pure short circuit is the only type of short circuit. Tech B says that a short causes abnormally high current flow in the circuit and may cause the circuit protection devices to open the circuit. Who is correct?
Tech B.
Tech A says that if a 12-volt light has 10 amps flowing through it, it is using 22 watts of electricity. Tech B says that watts are units of electrical power. Who is correct?
Tech B.
Two technicians are discussing a series circuit with four resistors of various resistances. Tech A says that current flow is different in each resistor. Tech B says that current flow is the same in each resistor. Who is correct?
Tech B.
Energy.
The ability to do work.
Voltage drop.
The amount of potential difference between two points in a circuit.
Current flow.
The flow of electrons, typically within a circuit or component.
Hot junction.
The heating point of a thermocouple.
Ground.
The return path for electrical current in a vehicle chassis, other metal of the vehicle, or dedicated wire.
The PN junction of a semiconductor is located in the __________ layer.
depletion
The unit of __________ __________ is the watt.
electrical power
When two dissimilar metals are immersed in an electrolyte, the breakdown of chemicals into charged particles that results in a flow of electricity is called __________.
electrolysis.
A(n) __________ is constructed by winding a conductor wire many hundreds of thousands of times, around a soft iron or metal core and passing current through the coil.
electromagnet
Electromotive force can be best described as the:
force of attraction/repelling which drives the electrons to move along.
One __________ is produced when 1 volt causes 1 amp of current to flow.
ohm
The device which is used to measure the amount of resistance in a component or a circuit is a(n):
ohmmeter.
The term __________ describes a low-voltage circuit that does not have a complete circuit and therefore cannot conduct current.
open.
In a(n) __________ circuit, all components are connected directly to the voltage supply.
parallel.
The rate of transforming energy is also known as __________.
power.
A __________ is an electromechanical switching device whereby the magnetism from a coil winding acts on a lever that switches a set of contacts.
relay.
Electrical __________, measured in ohms, affects the current flow in a circuit.
resistance
The degree to which a material opposes the passage of electrical current through it is called:
resistance.
In its purest definition, the term __________ describes a circuit fault in which current takes a shorter path, resistance-wise, through an accidental or unintended route.
short
Insulator.
A material that has properties that prevent the easy flow of electricity. These materials are made up of atoms with five to eight electrons in the valence ring.
Semiconductor.
A material used to make microchips, transistors, and diodes.
Sine wave.
A mathematical function that describes a repetitive waveform such as so alternating current signal.
Silicon.
A material commonly used to make semiconductors.
If a person has a 4 ohm resistor and the battery is charged to 12 volts, how many amps will flow in the circuit?
3 amps.
If a 15-volt circuit with a single light has a current flow of 2 amps, then what is the power in watts in the circuit?
30.
Electromagnet.
A conductor wound in a coil that produces a magnetic field when current flows through it.
Ammeter.
A device used to measure current flow.
All of the following statements describing the basic principles of electricity are true except:
A positive ion exerts a repelling force on the extra electron.
Alternating curve. (AC)
A type of current flow that flows back and forth.
Insulators:
A. Conductor. B. Insulator. C. Semiconductor.
Short circuit:
A. High current terminals. B. Low current terminals. C. Short in windings. D. Iron core. E. Contact points. F. Coil wings.
Ions:
A. Negative ion. B. Positive ion.
Parts of an atom (including charge):
A. electrons Charge negative B. protons Charge positive C. neutrons Charge negative
Which of the following Ohm's law formulas is correct?
All of the above.
Short.
Also called a short circuit, the flow of current along an unintended route.
Which of the following is a measure of the number of electrons flowing past a given point in 1 second.
Amp. (ampere)
Amp.
An abbreviation for amperes, the unit for current measurement.
What is meant by the term "continuity"?
An electrical circuit that has a continuous and uninterrupted connection.
Relay.
An electromechanical switching device whereby the magnetism from a coil winding acts on a lever that switches a set of contacts.
Polarity.
The state of charge, positive or negative.
Hole theory.
The theory that as electrons flow from negative to positive, holes flow from positive to negative.
Electron theory.
The theory that electrons, being negatively charged, repel other electrons and are attracted to positively charged objects; thus electrons flow from negative to positive.
Ohm.
The unit for measuring electrical resistance.
Volt.
The unit used to measure potential difference or electrical pressure.
A deficiency of electrons gives an atom an overall positive charge.
True
A light bulb uses a certain amount of electrical power, but the power used is not an indication of brightness.
True
A typical incandescent light bulb creates light, but only about 10% of the electricity is converted to light; about 90% is wasted as heat.
True
Hertz is the measurement of frequency and indicates the number of cycles per second.
True
If voltage stays the same and resistance doubles, half as much amperage can be pushed through the resistance.
True
Most wiring diagrams are written from the conventional theory perspective, while electronic circuits are typically designed and operate on the electron theory perspective.
True
Ohm's law is a relationship between volts, amps, and ohms and because they must always balance out, if we know any two of the values, then we can calculate the third.
True
Volts, amps, and ohms are three basic units of electrical measurement.
True
What can be the number of valence ring electrons of conductors?
Two. (1-3 for classification.)
All of the following statements describing an electrical circuit are true except:
When the switch is moved to closed position, the current path is broken and current flow stops. (In a closed circuit, current flow continues!)
When two dissimilar metals are immersed in an acidic liquid, the breakdown of chemicals into charged particles results in a flow of electricity. This principle is used in a(n):
battery.
The transfer of electrical energy from one coil to another through induction in a transformer is known as __________ __________.
transformer action.
Electrochemical energy is produced when __________.
two dissimilar metals are immersed in an acidic liquid.
Electromotive force is also referred to as __________.
voltage.
The force with which the positive terminal pulls the free electrons toward it in a circuit is measured to:
volts.
The electrical resistance of a circuit is measured in __________.
Ω. (ohms)
