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ASVAB Electronics Questions and Answers.
Electricity - General term for the variety of phenomena resulting from the presence and flow of electric current Volts Amperes (amps) Ohms - 3 ways Electricity is measured Volts - Measure the difference of potential between 2 points Amperes (amps) - Measure the number of electrons that move past a specific point in 1 second (i.e. electrical currents) Ohms - Measure resistance, including anything that could limit the flow of electrons Current - Electrical ___ occurs when electrons move from one place to another. Conductors (e.g. copper, silver, water) - A substance, body, or device that conducts electricity; allows the electrons to move freely. Insulators (e.g. rubber, wood) - A material of such low conductivity that does not easily allow the flow of electrical current to pass through it; discourages electrical current Watt - This measures power, the rate at which electrical energy is consumed or transformed into another type of energy, such as light or heat Power - The rate at which electrical energy is consumed or transformed into another type of energy, such as light or heat Watt-hour - This is the amount of energy used in 1 hour at a rate of 1 watt. Kilowatt-hour - The amount of energy used in 1 hour at a rate of 1,000 watts(i.e.1- kilowatt)
True - True or False Most electricity is measured in kilowatt-hours Wattage x Time (expressed in hours) - To find watt-hours multiply ___ by ___. 10 kilowatt-hours - How many kilowatt-hours is enough energy to run a 10,000-watt speaker system for 1 hour? 2 hours - 10 kilowatt-hours is enough energy to run a 5,000-watt air conditioner for how long? 10 hours - 10 kilowatt-hours is enough energy to run a 1,000-watt waffle iron for how long? Circuit - The path of an electrical current Open - When there is literally an open space in the circuit that prohibits current from flowing Short - When the open space of a circuit has been closed to allow current to flow Voltage - The difference of the pressure between 2 points in a circuit (sometimes called voltage drop or difference of potential) True - True or False To see what the voltage is anywhere in a circuit, you have to compare the voltage at that point to ground Ground (e.g. base of a lamp, chassis of a car) - Any part of a circuit (or other object that has electricity running through it) that measures 0 volts Voltmeter or multimeter - Measures voltage in a circuit Voltmeter - An instrument used for measuring electrical potential difference between two points in an electric circuit (i.e. voltage)
Ohmmeter - Device that measures the amount of resistance that interferes with the flow The amount of voltage (measured in volts) The resistance to the current (measured in ohms) The amount of current (measured in amps) - The 3 influences that are present when current flows through a wire The current in a circuit is directly proportional to the applied voltage and inversely proportional to the circuit resistance. - What is Ohm's law I - Abbreviation for current E - Abbreviation for voltage R - Abbreviation for resistance Current (amperes) = Voltage(volts)/Resistance(ohms) OR I = E / R - Formula to solve for Current (Ohm's law) Voltage = Current x Resistance OR E=IR - Formula to solve for Voltage (Ohm's law) Resistance = Voltage/Current OR R = E / I - Formula to solve for Resistance (Ohm's law) Watts - Unit of power in the International System of Units (SI) 750 watts - How many watts are to 1 horsepower True or False - One kilowatt represents 1,000 watts By multiplying the number of kilowatts (kW) required by the number of hours of use. (e.g. if you use a 40-watt light bulb 5 hours a day, you've used 200 watt-hours, or 0. killowatt-hours of electrical energy) - How are kilowatt-hours determined?
Least - Electricity follows the path of ___ resistance. Conventional Current - The vacancies left by electrical particles "moving" from the positive (+) terminal to the negative (-) terminal of a battery. (in regards to electrical flow of current) True - True or False The military teaches current flow based on the flow of the electrons, and electrons, no matter how you look at it, flow from the negative terminal to the positive terminal Short circuit - This occurs when any wire accidentally crosses over another wire, causing the electricity to bypass the rest of the circuit and not follow the intended path Chemical Effect Heat Effect Magnetic Effect Physiological Effect - 4 effects produced by current and some of their commercial applications Chemical Effect - Current produces this effect when it passes through a chemical compound and breaks that compound up. (Also called Electrolytic Decomposition, this phenomenon is used in Electroplating) Electroplating - A process used to cover objects with a very thin coating of metal. (chemical effect) Heat Effect - Conducting electricity causes wires to become heated. Heat develops because the current must overcome the resistance of the wire. This heat energy can be quite obvious or hardly noticeable to touch, depending on the size of the wire and the amount of current Magnetic Effect - When a wire is introduced into a magnetic field, electricity flows through the wire and creates a magnetic field that repels a magnet. This effect is used to create energy through Electromagnetic Induction. If the wire is wrapped around an iron core and a current is sent through the wire, the iron become magnetized. Electromagnetic Induction - The production of electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, etc.
Impedance = Electromotive force / Current - Formula for Impedance Capacitors and Inductors - Devices used in circuits to provide the type of reactance needed. Microfarad (μF) - Capacitors are rated in ___. Millihenries (mH) - Inductors are rated in ___. Rectification - The process of making certain electronic circuits change alternating current to direct current. (i.e. changes incoming AC to DC) Rectifiers - The circuits that perform rectification Semiconductor Diodes - Found in rectifiers; a component made of a material with conductivity somewhere between that of a conductor and an insulator Diodes - These conduct electricity in only one direction. Inductors and Capacitors - Rectification often requires ___ and ___. Cooler Variable - Rectification helps appliances run at ___ temperatures and allows them to run at ___ speeds. Direct - Devices typically need ___ current to run properly. Semiconductor - An object that conducts electricity poorly at low temperatures. Transistor - A semiconductor that controls the flow of electricity in a circuit. Usually made of germanium or silicon. This electrical device can amplify a signal. True - True or False Transistors are small, require little power, and last a long time Emitter
Base Collector - 3 terminals a transistor contains Emitter - The voltage output (transistor) Base - This acts like a gate, and the voltage at the base controls the flow of current through the transistor (and therefore the voltage) Collector - The voltage input (transistor ) Block diagrams - Used to show the various combined circuits that form a complex system Wires - Used to pass current from one part of the component to another Joined wires - Wires that are connected to each other and are indicated by a dark circle in diagrams Unjoined wires - Wires that are not connected; in circuit diagrams, it is necessary to draw wires crossing even though they aren't connected, this is indicated by a hump symbol Cell - This supplies electrical current. Battery - Has 2 or more cells. The large terminal is positive DC Power Supply - This provides direct current; direct current always flows in 1 direction AC Power Supply - This provides alternating current; alternating current constantly changes direction at a specific frequency Fuse - A safety device that blows (melts) if the current flowing through it exceeds a specified value Transformer - Consists of 2 coils of wire linked by an iron core. These are used to step up (increase) and step down (decrease) AC
doorbell Push-to-break switch - With this switch, the circuit is normally closed (the device is on), and the circuit is open (device is off) only when the button is pressed On/off switch - This switch allows current to flow only when it's in the closed (on) position Two-way switch - This switch directs the flow of current to one of two routes, according to its position Dual on/off switch - This type of switch is often used to switch the main electricity because it can isolate both the live and neutral connections Relay (relay switch) - An electrically operated switch that may operate multiple switches at one time. Current flowing through a coil sets up a magnetic field, which causes the lever(s) to move, effectively changing the (relay) switch's position(s) Resistor (nonvariable) - Restrict the flow of electric current. True - True or False Resistors are rated in ohms and have a color code on them to indicate their value, tolerance, and sometimes quality. 0 - Black is __. (band code) 1 - Brown is __. (band code) 2 - Red is __. (band code) 3 - Orange is __. (band code) 4 - Yellow is __. (band code)
5 - Green is __. (band code) 6 - Blue is __. (band code) 7 - Violet is __. (band code) 8 - Gray is __. (band code) 9 - White is __. (band code) First Second - The ___ and ___ bands on the resistor are the first 2 digits in the resistor's value. Third - The ___ band indicates the multiplier (number of zeros after the first two numbers). 24000 ohms - If the first band is red, the second is yellow, and the third band is orange, the resistor's value is ___ ohms. True - True or False A gold or silver band after the first bands indicates tolerance, and a quality band may follow the tolerance band. Variable resistor - Restrict the flow of electric current. Rheostat Potentiometer Preset variable resistor - Types of variable resistors Rheostat - Type of variable resistor with 2 contacts, usually used to control
Amperes (amps) - Unit of measure for current Volts - Unit of measure for voltage Ohms - Unit of measure for resistance Watts - Unit of measure for power Watt-hours - Unit of measure for energy
