# Shared Flashcard Set

## Details

Airframe and Powerplant
Electrical Oral questions
61
Aerospace Engineering
Not Applicable
05/19/2015

Term
 What constitutes a capacitor and what determines the capacitance?
Definition
 2 conductors separated by an insulator.   capacitance is determined by area of the plates, amount of seperation between the plates, and the kind of insulating dielectric between the plates.
Term
 What is the purpose of a capacitor?
Definition
 Stores electrical energy in electrostatic fields. In an AC circuit it drops voltage and shifts the phase of current.
Term
 Does a capacitor cause current to lead or lag voltage in an AC circuit?
Definition
Term
 Why should electrolytic capacitors not be used in AC circuits?
Definition
 because they are polarized and will only pass current of one polarity and block the other one.
Term
 What is inductance and what is it measured in?
Definition
 Ability to store electrical energy in electomagnetic fields.     measured in HENERY
Term
 example of an inductor used in a magneto?
Definition
 Coil
Term
 Does and inductor cause the current to lead or lag the voltage?
Definition
 lag
Term
 What is it meant to impedance and what is it measured in?
Definition
 Total opposition to the flow of alternating current. its the sum of resistance capacitive reactance and inductive reactance.   Measured in ohms
Term
 5 sources of electrical energy
Definition
 magnetism-generators and alternators chemical energy-flashlight batterys light-solar cells heat-thermocoupler pressure
Term
 Basic unit of power in DC circuit
Definition
 WATT
Term
 what is meant by Kilowatt and megawatt?
Definition
 1,000   1,000,000
Term
 formula for power in a DC circuit
Definition
 P=ExI
Term
 relationship between mechanical and electrical power.
Definition
 1HP=746watts
Term
 What is true power in an AC circuit? What is it expressed in?
Definition
 product of the circuit voltage and the current that is in phase with this voltage.   Expressed in WATTS
Term
 What is apparent power in an AC circuit. how is it expressed?
Definition
 Product of the circut voltage and the circuit current.   Expressed in volt-amps
Term
 what is reactive power in an ac circuit and how is it expressed?
Definition
 power consumed in the inductive and capacitive reactances in an AC circuit.   expressed in volt-amps reactive or kilovolt-amps reactive
Term
 what is the power factor in an AC circuit?
Definition
 ratio of true power to apparent power.   ALSO   ratio of circuit resistance to circuit impedance
Term
 Most important law of electricty?
Definition
 Ohms Law
Term
 what elements make up Ohms Law
Definition
 E I R
Term
 what is voltage and what is the basic unit of voltage?
Definition
 electrical pressure   VOLT
Term
 What instrument is used to measure voltage?
Definition
 volt meter
Term
 when measuring voltage is a volt meter placed in series or parallel with the source of voltage
Definition
 parallel
Term
 what is electrical current and whats the basic unit ?
Definition
 flow of electrons in a circuit    basic unit is the AMP
Term
 what instrument is used to measure current flow?
Definition
 ammeter
Term
 2 things that happen when current flows through a conductor
Definition
 heat is generated and a magnetic field surround the conductor.
Term
 to meassure current is the ammeter placed in parallel or in series with the component?
Definition
 series
Term
 what is meant by resistance in an electrical circuit and whats the basic unit
Definition
 opposition to the flow of electrons   OHMS
Term
 what is an megaohm
Definition
 1,000,000 ohms
Term
 four things that affect the resistance of an electrical conductor?
Definition
 the material cross sectional area length temperature
Term
 what instrument is used to measure electrical resistance?
Definition
 ohmmeter
Term
 how can you tell resistance of a composition resistor?
Definition
 series of colored bands around one end of the resistor
Term
 what is meant by continuity in an electrical resistor
Definition
 when electrons can flow smoothly from the terminal of the power source to the other
Term
 what instrument measures continunity
Definition
 ohmmeter
Term
 When measuring resistance should the circuit be energized?
Definition
 NO
Term
 3 things an electric cicuit must contain?
Definition
Term
 three types of DC circuits
Definition
 series parallel series-parallel
Term
 basic equation of ohms law
Definition
 E=I X R
Term
 What happens to the current in a DC circuit if the voltage is i ncreaded but the resistance remains the same?
Definition
 it increases
Term
 what happens to the current in a conductor if the length of the conductor is doubled with all other parameters unchanged.
Definition
 decrease to 1/2
Term
 what is meant by the capacity rating of a lead-acid battery?
Definition
 # of hours a battery can supply a given current flow
Term
 what units is batterys capacity expressed
Definition
 ampere hours
Term
 what electrolyte is used in lead acid battery
Definition
 mixture of sulfuric acid and water
Term
 does specific gravity of the electrolyte in a lead-acid battery increase or decrease as the battery becomes discharged.
Definition
 decreases
Term
 what is the specific gravity of a fully charged lead acid battery?
Definition
 between 1.275 and 1.300
Term
 how many cells in a 24volt lead acid battery
Definition
 12
Term
 range of temperatures of the electrolyte in a lead acid battery that does not require a correction when measuring its specific gravity?
Definition
 between 70-90 degrees F
Term
 what instrument is used to measure the specific gravity of the electrolyte in a lead acid battery?
Definition
 hydrometer
Term
 how do you treat a lead-acid battery compartment to protect it from corrosion?
Definition
 (tar base) paint of polyurethane enamel
Term
 what is used to neutralize spilled electrolyte from a lead-acid battery
Definition
 solution of bicarbonate of soda and water
Term
 How high should the elctrolyte level be in a properly serviced lead-acid battery?
Definition
 only up to the level of the indicator on the cell
Term
 what is the open circuit voltage of a lead acid cell?
Definition
 2.1 volts
Term
 what gases are released when a lead acid battery is being charged?
Definition
 hydrogen and oxygen
Term
 what precautions should be taken in the maintenance shop where both lead-acid and nickel cadmium batteries are serviced?
Definition
 2 types of batterys should be kept seperate and the tools used on one type should not be used on the other.
Term
 what electrolyte is used in nickel cadmium battery?
Definition
 potassium hydroxide and water
Term
 why do you not use a hydrometer to measure the state of charge in nickel-cadmium battery?
Definition
 electrolytes do not enter into the chemical changes that occur when the battery is charged or discharged.
Term
 is the electrolyte level of a nickel cadmium battery lowest when the battery is fully charged or fully discharged.
Definition
 fully discharged
Term
 what is the result of cell imbalance in a nickel cadmium battery?
Definition
 low internal resistance allows current to flow between the unbalanced cells and generate heat.
Term
 what is thermal runaway?
Definition
 large current flow allowed by low internal resistance causes the middle cells to produce more heat than they can dissipate.
Term
 how can thermal runaway be prevented?
Definition
 monitoring the temperature of the middle cells and controlling the charging current to prevent and excess of current flowing into the battery
Term
 how it is possible to know when a nickel-cadmium battery is fully charged?
Definition
 completely discharge the battery and give it a constant current charge to 140% of its ampere-hour capacity
Term
 what is used to neutralize spilled electrolyte from nickel cadmium battery?
Definition
 boric acid and water
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