Basic Electricity I - Study Course Test Prep, Exams of Basic Electronics

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Basic Electricity I - Study Course Test Prep

What is the smallest divisible element of matter?- CORRECT ANSWER atom What are the three components of an atom? lectron, proton, neutron Which components of the atom determine whether it is copper, carbon, or some other element? a. number of neutrons b. number of protons c. number of electrons Whal charactcristic of an atom causes an clement Lo be a good conductor? a. weak valence electron bonding b. strong valence electron bonding c. number of electrons d. number of protons - CORRECT ANS Which item is not a conductor? a. lin b. plastic c. copper d. steel - CORR! ANSWER. plastic Which item is not an insulator? a. glass b. plastic c. wood . aluminum d. aluminum - What is the electrical foree which causes current to flow called? - C electromotive force (EMF) What determines the required size of wire for a circuit? - CORRECT ANSWER current In what unit is electrical power expressed? - CORRECT ANSWER-watts How is electrical energy consumption calculated? - CORR. ANSWER-power x time The resistance of a wire depends on what four factors? - ‘material, length, cross section, and temperature What is the effect on a circuit when the wire diameter is reduced?- CORRECT ANS ER-curreni. carrying capacity is reduced The metallic elements all have the common characteristic that their valence electrons are CORRECT. rather ____ bonded to the atom - Valence electrons are the ___ electrons - C ANSWER outermost Insulators have valence electrons that are very tightly attracted to the ___ - CORRECT ANSWEF-nucleus Four factors that affect the resistance of a conductor are .. material, temperature, length, and cross-sectional area T or F: The relative resistance of a given material is called specific resistance or CORRECT ANSWER-true resistivity - Materials wilh low resisLlivity have low resistance Lo electron flow and they make good ___- CORRECT ANSWER-canductors Materials with high resislivity exhibit high resistance to electron flow and they make good -€ ANSWER insulators The greater the cross-sectional area of a conductor, the _____ the resistance (R) - CORRECT ANSWER lower The greater the length of a conductor, the ____ the resistance (R) ANSWER greater T or F: For long conductor runs we typically increase the diameter of the conductor in CORRECT order to keep the resistance of the conductor within desired limits - ANSWER-true ANSWER-higher Electrons are ____ charged particles - CORRECT ANSWEFR-negatively Electrons move from negative to positive and this is called ___ flow - CORRECT: ANSWERelectron The external force that tends to make electrons move through a conductor is known as force (EMF) or voltage potential - CORRECT ANSWER-electromotive Electromotive foree is measured and oxpressed in volts, and is commonly given the sytwmbol ____ in equations - CORRECT ANSWER-E Greater vollage in an clectrical circuit means current will flaw - CORRECT ANSWER-more The rate of movement of the electrons through a conductor is called - CORRECT ANSWER-current Current is measured and expressed in terms of (amps) - amperes Current is given the symbol ____for use in equations - CORRECT ANSWER 1 Electrical energy consumption is the amount of electrical work done and is usually CORRECT ANSWER-kilowatt expressed in terms of (kWh) - ANSWEF-direct current (DC) and ANSWER-one Alternating current continuously flow direction - CORR: ANSWER-reverses Hertz stands for___ per second - CORRECT ANSWER cycles T or F: frequency = cycles per second- CORRECT ANSWER-true The first law of thermodynamics says that energy can neither be created nor - oi /ER-destroyod Electrical utilities generate electrical power using hydro, wind, coal, nuclear and natural e use - CORRECT gas as energy sources to spin , which create the electricity A. gcncralors Accircuit can be defined as a___ for current to flaw- CORRECT ANSWER path You must have a (potential difference) and a completed circuit for current to flow - C ‘Rvoltage What tool can be used to find out why the load is not working? - CORRECT ANSWER- Voltmeter If there is full voltage across the load and the load is not responding, what is the load? - € ANSWER-Open In an electrical circuit, the current is directly proportional to the voltage applied, and inversely proportional to the ___ in the circuit - CORRECT ANSWER-resistance An electrical circuil consists of a source, a load, and a through which cleclrons can travel - CORRECT ANS T or F: The source supplies clectrical energy and the load converts that oncrgy Lo some other form - CORR’ Al ‘Retrue ANSWER-true power Tt is the amount of energy used in a given time... - € Power, for electrical purposes, is expressed in watts or horsepower The direction in which a free north pole would tend to move in the presence of a magnetic field is called the___ - CORRECT ANSWER-positive direction Air and copper offer resistance to the path of flux lines. This resistance is known as - CORRECT ANSWER reluctance The permeability of a substance is defined as__ - CORRECT. ANSWER-the ratio of the number of flux lines passing through a substance as compare to air The fact that an electric current in a conductor is always surrounded by a magnetic field was discovered by ___ - CORRECT ANSWER-Oersted Small groups of uncompensated electron spins in a magnetic material spinning in the saine direction are callod - CORR! ‘ER-domains The Right Hand Rule determines ___ - CORRECT ANSWER-magnclic ficld direction the product of the turns and the current An electromagnet’s strength will be increased by ____ - CORRECT ANSWER- increasing the number of coil turns Voltage in a transformer is Faraday's Law states voltage is directly proportional to the force A current set up by an induced voltage always tends to create a flux in such a direction aS LO - CORRECT ANSWEF-oppase any change in the existing flux Thermocouple output depends on - “pe of dissimilar metals and temperature difference between Junctions proportional to the applied light cnergy Piezoclectricity is clectron flow created by -€ Electron flow can occur from ___ - CORRECT ANSWER-the zine clectrade Lo the carbon electrode When the conductor moves downward through the magnetic field, the galvonometer needle - CORR! Maximum voltage is generated when the rotating loop ___ - CORRECT ANSWER-cuts through the maximum lines of magnetic flux Generated voltage is directly proportional to the rate at which a conductor ___ - CORRECT ANSWEF-is cutting magnetic lines of force What advantage is gained in a three-phase four-wire delta system over a three-phase tem? - CORR! three-wire sy: WER-a separate lower voltage is available Three-phase power is preferable to single-phase power because it provides - CORRECT ANSWEF-better motor starting and running characteristics A three-phase four-wire wye circuit with a phase to ground voltage of 120 volts has an approximate phase to phase potential of ____ - CORRECT ANSWER-208 volts How does a parallel circuit differ from a series circuit? a. parallel circuits are always made up of series circuits b. parallel cirenits are made of parallel branches into which the current divides from a common voltage source c¢. parallel circuits have only one path Lor the current Lo flow, unlike series circuils d. parallel circuits are made of parallel branches into which the voltage divides from a common voltage source - CORRECT ANSWER. parallel circuits are made of parallel branches into which the cur ront. divides from a common voltage souree Current division between branches of parallel circuits is affected by ... a. the magnitude of the resistance in each branch b. the magnitude of the current in the adjacent branch to the right c. the voltage in each branch d. the total voltage - CORRECT ANSWERa. the magnitude of the resistance in each branch If branches of a parallel circuit have different resistances, which of the following is a true statement? a. the voltage drop is directly proportional to the current times the voltage and the currents are all equal in parallel circuits b. the voltage drop in parallel circuits is the sum of the voltages across each branch c. the voltage drop in each branch is equal in parallel circuits d. there is no voltage drop in parallel circuits - ‘ANSWER. the voltage drop in each branch is equal in parallel circuits One way to calculate total current for parallel circuits is to ... a. multiply total voltage by individual resistance b. multiply the total resistance by the total voltage c. add together all of the branch circuit currents d. divide the product of all branch circuit currents by the sum of the branch circuit currents add together all of the branch cireuil. currents What is the first law of parallel cirenils? a. parallel circuits are easier to calculate than series circuits b. the same vollage drop occurs across cach branch c. the total current in a parallel circuit is equal to the product of the currents flowing in the individual branches d. parallel circuits are the same as series circuits - b. the same voltage drop occurs across each branch Which cirenit type, scries or parallel, acts as a voltage divider ... a. parallel circuits divide voltage across each branch How is the total resistance of a circuit affected as additional resistive branch circuits are added in parallel? a. increased b. decreased ¢. is proportional to the voltage at is source When does the current returning to the source of EMF always equal the current leaving the source? a. in parallel circuits only b. in series circuits only ¢. in all parallel circuits and series circuits Tf all branch resistors are identical, how do we compute total resistance for a parallel circuit? a. by dividing the resistance by two b. by dividing the resistance of one branch by the number of parallel branches c. by adding the resistances together Just like a series circuit d. by subtracting branch resistances - CORRECT ANSWER. by dividing the resistance of one branch by the number of parallel branche: Which equation is known as ohin’s law? a. E=]2R b.E=IR c. P=IR d. P=ER- CORRECT ANSWER-b. E=IR Current leads voltage when the reactance is___ Current lags voltage when the reactance is - “inductive Which cquation is used Lo calculate powcr? a. P=IR b. P=E2R c. P=ER d. P=EI- CORRECT ANSWER-d. P = El What is the purpose of a transformer? - CORRECT ANSWER-it transforms AC electrical power from one circuit to another by mutual induct. What are the three principal parts of a transformer? - CORRECT ANSWER-primary winding, secondary winding, and core What is the fundamental electrical principal that makes the transfer of power ina lransformer possible? - CORRECT ANSWER-muuual induction The ratio belween primary and secondary vollage is the ralio between the primary and secondary windings - CORRECT ANSWER-the same as What determines the current flow in the primary circuit of a transformer? - CORRECT current in the secondary Ina step down transformer, the current in the primary windings is____ the current in the secondary windings - CORRECT ANSWER-less than Ina signal current transformer, the current in the primary is the current in the ANSWER-less than secondary circuit - CORR! What types of voltages can a transformer be used for? - CORRECT ANSWER-AC voltages only Why is transformer phasing important? - CORR: ANSWER+o avoid transformer burnout What is a practical check for correct transformer phasing? - CORRECT ANSWEI-use an AC volt meter to determine if the transformers are phased c RECT What pracucal check would indicate an incorrectly phased Lransformer? - C ANSWER-secondary voltage is too high If the primary winding of a transformer has 100 turns and 120 volts, what voltage is induced in the secondary windings with 400 turns? AB) VF In a typical residential application, the difference in voltage between an earth ground and one leg of a 240 volt circuit is ... a. 9 volts b. 120 volts c. 240 volts d. 480 volts - CORRECT. Reb. 120 volts The service drop is ... a. Iho fuse box b. the wires bringing power to a building c¢. everyLhing owned by the clectric company d. always 240 volts - CORREC The minimum safety provisions for motor circuits are provided in the ... a. National Electric Code b. Underwriters Code c. utility handbooks d. state and local codes - CORRECT ANSWEF-a. National Electric Code What type of building is served by a single-phase threo-wire circuil? a. a warehouse b. a substation c. a home d. a power plant - CORRECT ANSWER-c. a home Grounding is important to an electrical system because ...