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81 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What constitutes a capacitor |
Two conductors separated by an insulator |
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What is the purpose of a capacitor |
It's stores electrical energy in electrostatic fields |
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Does a capacitor in an AC circuit causes the current to lead or lag the voltage |
It causes the current to lead the voltage |
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What is the basic unit of capacitance |
The farad |
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Why should electrolytic capacitors not be used in an AC circuit |
They are polarized. An electrolytic capacitor it will pass current of one polarity but will block current of the opposite polarity |
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What is meant by inductance |
Voltage is induced by magnetic flux lines in a coil in an AC circuit. The induced voltage is opposite in direction to the applied voltage and opposes any change in the alternating current |
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What is the basic unit of inductance |
The Henry |
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What is an example of an inductor used in a Magneto |
The coil |
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Does an inductor in an AC circuit cause current to lead or lag the voltage |
It causes the current to lag behind the voltage |
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How can you find the polarity of an electromagnet |
Hold the electromagnet in your left hand with your fingers encircling the coil in the direction electrons flow (from negative to positive). your thumb will point to the North Pole of the electromagnet |
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What is impedance |
The total opposition to the flow of alternating current. It is the vector sum of resistance, capacitive reactance, and inductive reactance. |
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In what units is impedance measured |
In ohms |
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What are five sources of electrical energy |
Magnetism, chemical energy, light, heat, and pressure. |
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What is the basic unit of power in a DC circuit |
The watt |
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What is meant by a kilowatt |
1000 Watts |
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What is meant by a megawatt |
1 million Watts |
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What is the formula for power in a DC circuit |
Power = current times voltage (P = I × E) |
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What is the relationship between mechanical and electrical power |
1 horsepower equals 746 Watts |
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What is meant by true power in an AC circuit |
The product of the circuit voltage and the current that is in Phase with this voltage |
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In what units is true power expressed |
In Watts |
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What is meant by Apparent power in an AC circuit |
The product of the circuit voltage and the circuit current |
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In what units is apparent power expressed |
In volt-amps |
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What is meant by reactive power in an AC circuit |
The power consumed in the inductive and capacitive reactances in an AC circuit. reactive power is also called wattless power. |
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In what units is reactive power expressed |
In volt-amps reactive (VAR), or kilovolt-amps reactive (KVAR) |
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What is meant by power factor in an AC circuit |
The ratio of true power to apparent power . it is also the ratio of circuit resistance to Circuit impedance |
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Which law of electricity is the most important for an aircraft mechanic to know |
Ohm's law |
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What are the elements of Ohm's law |
Voltage (E) current (I) and resistance (R). volts, amps and ohms |
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What is voltage |
Electrical pressure |
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What is the basic unit of voltage |
The Volt |
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What instrument is used to measure voltage |
A voltmeter |
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To measure voltage, is a voltmeter placed in series or in parallel with the source or voltage? |
In parallel |
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What is electrical current |
The flow of electrons in a circuit |
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What is a basic unit of current flow |
The ampere, the amp. |
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What part of an amp is a milliamp |
One thousandth of an amp (0.001) |
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What instrument is used to measure current flow |
An ammeter |
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What two things happen when current flows through a conductor |
Heat is generated and a magnetic field surrounds the conductor |
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To measure current through a component, is an ammeter placed in parallel or in series with a component |
In series |
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What is meant by resistance in the an electrical circuit |
The opposition to the flow of electrons |
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What is the basic unit of electrical resistance |
The ohm |
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What is a megaohm |
1 million ohms |
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What four things affect the resistance of an electrical conductor |
The material, the cross-sectional area, the length and temperature |
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What instrument is used to measure electrical resistance |
An ohmmeter |
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How can you tell the resistance of a composition resistor |
By a series of colored bands around one end of the resistor |
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What is meant by continuity in an electrical circuit |
The circuit is continuous or complete when electrons can flow from one terminal of the power source to the other |
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What instrument is used to measure continuity in an electrical circuit |
An ohmmeter |
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When measuring resistance of a component with an ohmmeter should the circuit be energized? |
No, there should be no power on the circuit |
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What three things must an electric circuit contain |
A source of electrical energy, a load to use the energy, and conductors to join the source and the load. |
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What are three types of d c circuits with regard to the placement of the various circuit components |
Series, parallel, and series-parallel |
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What is the name of the law that describes the relationship in an electrical circuit of voltage current and resistance |
Ohm's law |
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What is the basic equation of Ohm's law |
E equals i x r |
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What formula is used to find current when voltage and resistance are known |
I=E/R |
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What formula is used to find resistance when voltage and current are known |
R=E/I |
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What happens to the current in a DC circuit if the voltage is increased but the resistance Remains the Same |
It increases |
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What happens to the current in a conductor if the length of the conductor is doubled with all other parameters unchanged |
It would decrease to 1/2 |
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What is the voltage across each resistor connected in parallel across a 12 volt battery |
12 volts |
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How much current flows through each of three resistors connected in series if the total current is 3 amps |
3 amps |
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What is the total resistance of 3 12 ohm resistors connected in series |
36 ohms |
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What is the total resistance of three 12 ohms resistors connected in parallel |
4 Ohms |
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What is meant by the capacity rating of a lead acid battery |
The number of hours a battery can supply a given current flow |
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In what units is battery capacity expressed |
In ampere hours |
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What electrolyte is used in a lead acid battery |
A mixture of sulfuric acid and water |
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Does the specific gravity of the electrolyte in a led acid battery increase or decrease as the battery becomes charged |
It decreases |
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What is the specific gravity of a fully charged lead acid battery |
Between 1.275 and 1.300 |
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How many cells are there in a 24 volt lead acid battery |
12 |
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What is the range of temperatures of the electrolyte in a led acid battery that does not require a correction when measuring its specific gravity |
Between 70 degrees Fahrenheit and 90 degrees Fahrenheit |
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What instrument is used to measure the specific gravity of the electrolyte in a lead acid battery |
A hydrometer |
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How do you treat a led acid battery compartment to protect it from corrosion |
Paint it with an asphaltic tar based paint or with a polyurethane enamel |
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What is used to neutralize spilled electrolyte from a led acid battery |
A solution of bicarbonate soda and water |
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How high should the electrolyte level be in a properly serviced led acid battery |
Only up to the level of the indicator in the cell |
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Why is the closed circuit voltage of a led acid battery lower than its open circuit voltage |
Voltage is dropped across the internal resistance of the battery |
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What is the open-circuit voltage of a lead acid cell |
2.1 volts |
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What gases are released when a led acid battery is being charged |
Hydrogen and oxygen |
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What precautions should be taken in the maintenance shop where both led acid and nickel cadmium batteries are serviced |
The two types of batteries should be kept separate, and the tools used on one type should not be used on the other |
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What is the electrolyte used in A nickel cadmium battery |
Potassium hydroxide and water |
Bananna |
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Why is a hydrometer not used to measure the state of charge of a nickel cadmium battery |
The electrolyte of a nickel cadmium battery does not enter into the chemical changes that occur when the battery is charged or discharged. its specific gravity does not change appreciably |
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Is the electrolyte level of a nickel cadmium battery lowest when the battery is fully charged or fully discharged |
Fully discharged |
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What is a result of cell imbalance in a nickel cadmium battery |
The low internal resistance allows current to flow between the unbalanced cells and generate Heat |
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What is a thermal Runaway |
The large current flow Allowed by the low internal resistance causes the middle cells to produce more heat than they can dissipate. the heat further lowers the internal resistance so more current can flow. this continues until the battery destroys itself |
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How May Thermal runaway be prevented |
By carefully monitoring the temperature of the metal cells and controlling the charging current to prevent an excess of current flowing into the battery |
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How is it possible to know when a nickel-cadmium battery is fully charged |
Completely discharge the battery and give it a constant-current charge to 140% of its ampere-hour capacity |
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What is used to neutralize spilled electrolyte from a nickel cadmium battery |
A solution of boric acid and water |
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