electronics
Electricity is defined as
(A) the acceleration of electrons toward protons.
(B) the flow of electrons along a conductor.
(C) the movement of charged metallic atoms to a lower-density area.
(D) the flow of protons along a conductor.
(B) Electricity is defined as the flow of electrons along a conductor. Electricity usually flows around a circuit from a negative terminal to a positive terminal.
Free electrons
(A) have left their original orbits and move from atom to atom at random.
(B) do not exist.
(C) are captured by atoms with the same kind of charge.
(D) help balance atoms that are short of protons.
(A) Free electrons have left their original orbits and move from atom to atom at random.
Free electrons are usually influenced by an applied electric or magnetic field.
The atoms of each element have a specific number of__ and ___number of ___
(A)neutrons, a higher; protons
B) electrons, a lower, protons
(C)protons, the same, neutrons
(D) electrons, the same, protons
(D) The atoms of each element have a specific number of electrons and the same number of protons. The atomic number for an element (listed in the Periodic Table on page 129 at the top of an element's block) is the number of protons in one atom of that element. If the number of protons in an atom changes, the atom becomes a different element. However, when an atom loses or gains electrons, it becomes an ion, an atom with an electrical charge.
4. Conventional current flow is
(B) an outmoded scientific concept.
(A) the theory that positive charges move from positive to negative.
(C) still found in many textbooks.
(D) all of the above.
(D) Conventional current flow is all of the above. The theory states that positive charges move from positive to negative. Conventional current flow is an outmoded scientific concept but is still found in many textbooks.
5. The magnitude of electrical current is measured in
(A) volts.
(B) ohms.
(C) coulombs.
D) amperes (amps).
(D) The magnitude of electrical current is measured in amperes (amps). Volts measure voltage; ohms measure electrical resistance in a circuit; and coulombs measure electrical charge
What is 1 coulomb per second equal to?
(A) 1 megawatt
(B) 1 volt
(C) 1 joule
(D) 1 ampere (1 amp)
(D) 1 coulomb per second is equal to 1 ampere (1 amp). A coulomb is 6.25 × 1013 electrons. Current is the flow of electrons, and an ampere (usually shortened to "amp") is a specific unit of current flow.
1. A conductor of electricity has___and___
(A) free electrons, offers little resistance to electron flow
(B) free protons, offers little resistance to proton flow
(C) no free electrons, helps move positive charges toward negative charges
D) free electrons, helps move positive charges toward negative charges
1. (A) A conductor of electricity has free electrons and offers little resistance to electron flow. Copper and silver are good examples of conductors. In fact, many conductors are metals.
As the diameter of electrical wire __, the gauge number___
(A) increases, increases
(B) decreases, decreases
(C) increases, stays the same
(D) decreases, increases
the gauge number
(D) As the diameter of electrical wire decreases, the gauge number increases. This is similar to many other nonmetric gauging systems but is unlike the metric wire size standard used in most parts of the world. The American Wire Gauge (AWG) system, used since 1857, originally referred to the number of passes through drawing dies that a certain diameter wire required; finer wires required more passes.
3. If a material has___ , it will be a good conductor of electricity.
(A) few free electrons
(B) many free electrons
C) many free protons
D) few free protons
(B) If a material has many free electrons, it will be a good conductor of electricity.
Materials such as__,__,__,and ___ are such poor electrical conductors that they are classified as insulators.
(A) glass, wet wood, rubber, some plastics
(B) rubber, glass, lead, paper
(C) rubber, glass, gold, some plastics
(D) glass, dry wood, rubber, some
4. (D) Materials such as glass, dry wood, rubber, and some plastics are such poor electrical conductors that they are classified as insulators. In these types of materials, the atoms'® electrons are tightly bound, as compared to good conductors. In insulators, therefore, the electrons do not move between atoms very easily, virtually stopping the flow of electrons.
Resistors are the opposite of
(A) bad conductors.
(B) good conductors.
(C) insulators.
D) semiconductors.
5. (B) Resistors are the opposite of good conductors. Resistors are materials through which electricity can flow but only with some difficulty. The difference among conduc-tors, resistors, and insulators is only a matter of degree - even good conductors have some resistance
Power is defined as
(A) the amount of effort needed to move 1 kilogram a distance of 1 foot in 1 minute.
(B) the rate at which work is done or weight is moved.
(C) only an electrical measurement.
D) only a mechanical measurement.
(B) Power is defined as the rate at which work is done or weight is moved.
2. W- is the symbol for
(A) a conductor.
(B) an open switch.
(C) a resistor.
(D) a power source.
2. (C) -W- is the symbol for a resistor. The symbol for a wire that conducts electricity is a simple line ——. The symbol for an open switch is —
-. There are several
symbols for a power source, depending on whether it is AC, DC, or a battery.
Resistance
(A) varies directly with the length of the wire.
(B) increases proportionately with the cross section of the wire.
(C) depends on only the material and the temperature of the conductor.
(D) remains the same for a certain conductor material regardless of size.
(A) Resistance varies directly with the length of the wire. Resistance also varies inversely with the square of the wire's diameter.
4. The opposite of resistance is
(A) dissipation.
(B) wattage.
(C) energy storage.
(D) conductance.
(D) The opposite of resistance is conductance.
The strength of an electrical current is___ to the voltage and __ to resitance
(A) directly proportional, inversely proportional
(B) inversely proportional, directly proportional
(C)unrelated, directly proportional
(D) directly proportional, unrelated
(A) The strength of an electrical current is directly proportional to the voltage and inversely proportional to the resistance.
Resistance, which is the tendency for a substance to oppose the flow of electrons, is measured in
(A) amps.
(B) watts.
(C) ohms.
(D volts.
(C) Resistance, which is the tendency for a substance to oppose the flow of electrons, is measured in ohms. This measurement is named in honor of German physicist George
A(n)__ is required for the controlled movement of electrons along a conductor.
(A) open
(B) complete
(C) series
(D) parallel
(B) A complete circuit is required for the controlled movement of electrons along a conductor. You can illustrate this with a string of lightbulbs. If one is burned out, or if the wire is broken somewhere along the line, all of the lightbulbs stop working.
2. In a series circuit, the sum of all voltages across resistors is
(A) greater than the applied voltage.
(B) equal to the applied voltage.
(C) less than the applied voltage.
D) inversely proportionate to the applied voltage.
2. (B) In a series circuit, the sum of all voltages across resistors is equal to the applied voltage. In other words, the total resistance of a series circuit is equal to the sum of the individual resistors.
3. A short circuit is
(A) two coils placed near one another.
(B) a combination of a series and a parallel arrangement.
(C) a path of lower resistance to electron flow that is usually unintentional.
D) a path of higher resistance to electron flow that is usually intentional.
3. (C) A short circuit is a path of lower resistance to electron flow that is usually unintentional. It is an accidental extra path for current to flow through and that has little to no resistance when compared with the intended circuit flow.
7. What is a "short"?
(A) An inductor that uses no power
(B) An interrupted circuit
(C) An undesired conductive path in a circuit
(D) A bare conductor
(C) A "short" is an undesired conductive path in a circuit.
8. Which of the following is represented by the symbol X,?
(A) source output level
B) coil reactance
(C) load impedance
(D) lowest threshold for filter excitation
(B) Coil reactance is represented by the symbol X,. The letter X combined with a subscript is the symbol for reactance. X, represents the reactance of inductive components, commonly called "coils." *c represents the reactance of capacitive
components.
Alternating current is produced
(A) through the interaction of magnetic fields and electric conductors.
(B) by the variable flux density coming from a stable magnetic field.
(C) by flipping a length of wire 180 degrees within a magnetic field.
(D) by an uninterrupted connection to the positive and negative poles of a power
(A) Alternating current is produced through the interaction of magnetic fields and electric conductors.
3. One complete cycle of a generator is called one
(A) ohm.
(B)hertz.
(C)amplitude.
(D)sine wave.
(B) One complete cycle of the generator is called one hert. An ohm is a unit of electrical resistance. Amplitude refers to the greatest difference of an alternating electrical current or potential from the average value. A sine wave is a curve that shows periodic oscillations of constant amplitude.
4. A transformer is used to
(A) step up or step down alternating current wattages.
(B) step up or step down direct current voltages.
(C) step up or step down alternating current voltages.
D) step up or step down direct current wattages.
(C) A transformer is used to step up or step down alternating current voltages.
__make it possible to store electric energy, as opposed to an electric
charge, in an electric field.
(A) Filters
(B) Capacitors
(C) Transformers
(D) Inductors
(B) Capacitors make it possible to store electric energy as opposed to an electric charge, in an electric field.
6. Static electricity is
(A) a theoretical concept used to balance equations.
(B) direct currect (DC).
(C) alternating current (AC).
(D) none of the above.
6. (D) Static electricity is none of the above. It is definitely not a theoretical concept used to balance equations. It is also neither AC nor DC, which are both currents- henceits accurately descriptive name, static electricity.
1. 120 V electrical power supply produces A to the load. The power that divered ls
(A) 60 ohms.
(B)60 watts.
(C)240 ohms.
(D)240 watts.
7. (B) A 120 V electrical power supply produces ≥
delivered is 60 watts. This is calculated using the formula P = El, where P equals power
in watts, Eis the electricity in volts, and I is the intensity in amperes.
8. A hertz (2) is a measurement of
(A) the number of times an AC current changes direction in 1 second.
(B) the number of times an AC current changes direction in 1 minute.
(C) the number of times a DC current changes direction in 1 second.
D) the number of times a DC current changes direction in 1 minute.
(A) A hertz (Hz) is a measurement of the number of times an AC current changes
9. A capacitor is a device that
(A) has no impact on circuit voltage.
(B) facilitates changes in circuit voltage.
(C) opposes any change in circuit voltage and continuously bleeds off electricity.
(D) opposes any change in circuit voltage and therefore stores electricity.
(D) A capacitor is a device that opposes any change in circuit voltage and therefore stores electricity.
1. A diode is a device
(A) that allows current to flow in one direction but not the other.
(B) that allows current to flow in either direction through the use of a switch.
(C) used to generate semiconductor minerals such as silicon and germanium.
D) used to control the voltage of current flow in one direction only.
1. (A) A diode is a device that allows current to flow in one direction but not the other.
Filter circuits
(A) purify the inputs to direct current circuits.
(B) reverse the polarity of output voltage.
(C) induce necessary pulsations into half-wave rectifier output.
(D)smooth out the pulsations of full-wave rectifiers.
(D) Filter circuits smooth out the pulsations of full-wave rectifiers.
The silicon-controlled rectifier (SCR) is used to
(A) divert current on its cathode-to-anode pathway.
(B) control current on its anode-to-cathode pathway.
(C) prevent short circuits.
D) replace thyristers.
B) The silicon-controlled rectifier (SCR) is used to control current on its anode-to-cathode pathway.
Which electrical component acts like a gate for electronic signals by regulating current and voltage?
(A) Transistor
(B) Battery
(C) Circuit breaker
(D) Resistor
. (A) A transistor acts like a gate for electronic signals by regulating current and voltage.
Many electrical circuits contain transistors.
1. A galvanic cell
(A) converts mechanical energy to chemical energy.
(B) converts chemical energy to potential energy.
C) converts electrical energy to chemical energy.
(D) converts chemical energy to electrical energy.
(D) A galvanic cell converts chemical energy to electrical energy. A galvanic cell (also known as a voltaic cell is an electrochemical cell that uses the transfer of electrons in oxidation-reduction reactions to supply an electric current. It generally consists of tro different metals connected by a salt bridge. A galvanic cell can instead be individual half-cells separated by a porous membrane.
2. Once a__
cell is discharged,___
(A) secondary, one or both electrodes are consumed so the cell is no longer usable.
(B) primary, one or both electrodes are consumed so the cell is no longer usable.
(C) polarized, electron flow can be reversed and the cell can be used again.
D) thyristor, electron flow can be reversed and the cell can be used again.
(B) Once a primary cell is discharged, one or both electrodes are consumed so the cell is no longer usable. In other words, a primary cell cannot be recharged.
An electric motor
(A) changes chemical energy into electrical energy for storage.
(B) changes electrical energy into mechanical energy to do work.
(C) changes electromechanical energy into torque to do work.
(D) changes potential energy into chemical energy to produce torque.
(B) An electric motor changes electrical energy into mechanical energy to do work.
__ check voltage,___check current and__,check resisitance
(A) Voltmeters, watt-hour meters, ohmmeters
(B) Voltmeters, ohmmeters, ammeters
(C) Voltmeters, ammeters, ohmmeters
(D) Voltmeters, ohmmeters, multimeters
(C) Voltmeters check voltage, ammeters check current, and ohmmeters check resistance.
Transducers convert___ to electrical energy
(A) sound, light, heat, or pressure
(B) chemical energy or pressure
(C) light, heat, or magnetism
(D) sine waves, pressure, or
(A) Transducers convert sound, light, heat, or pressure to electrical energy. Some common examples of transducers are microphones, loudspeakers, digital thermometers, and pressure sensors.
A battery is a device that
(A) converts mechanical energy to chemical energy.
(B) converts chemical energy to electrical energy.
(C)converts mechanical energy to electrical energy.
D) releases input-stored mechanical energy to an electrical
(B) A battery is a device that converts chemical energy to electrical energy.
The higher resolution of high-definition television (HDTV) as compared to a standard TV results from
(A) bigger scan lines.
(B) smaller gaps between scan lines.
(C) higher operating cycles.
D) the use of greater amounts of bandwidth.
7. (B) The higher resolution of high-definition television (HDTV) as compared to a standard TV results from smaller gaps between scan lines. These smaller gaps therefore allow more scan lines to be on the screen at one time (1,080 in an HDTV vs. 525 in a standard TV).