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General
BASIC ELECTRICITY
Question | Answer |
---|---|
What is the basic unit of voltage? | The volt. |
What is the basic unit of current? | The amp. |
What is the basic unit of resistance? | The ohm. |
Which law of electricity is the most important for an aircraft mechanic to know? | Ohm's law. |
What are the three elements in Ohm's law? | Voltage, current, and resistance (volts, amps, and ohms). |
What are five sources of electrical energy? | Magnetism, chemical energy, light, heat and pressure. |
What four things affect the resistance of an electrical conductor? | The material, the cross-sectional area, the length and the temperature. |
How can you tell the resistance of a composition resistor? | By a series of colored bands around one end of the resistor. |
What three things must all electrical circuits contain? | A source of electrical energy, a load to use the energy, and conductors to join the source and the load. |
What is the purpose of a capacitor? | To store electrical energy in electrostatic fields. |
What is the basic unit of capacitance? | The farad. |
Why should electrolytic capacitors not be used in an AC circuit? | They are polarized. An electrolytic capacitor will pass current of one polarity, but will block current of the opposite polarity. |
What is meant by inductance? | The ability to store electrical energy in electromagnetic fields. |
What is the basic unit of inductance? | The henry. |
What is meant by impedance? | The total opposition to the flow of alternating current. It is the vector sum of resistance, capacitive reactance and inductive reactance. |
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 the electrons flow. Your thumb will point to the north end of the electromagnet. |
In what units is impedance measured? | In ohms. |
What is the basic unit of electrical power in a DC circuit? | The watt. |
What is meant by a kilowatt? | 1,000 watts. |
What happens to the current in a DC circuit if the voltage is increased but the resistance remains the same? | The current increases. |
What are three types of DC circuits, with regard to the placement of the various circuit components? | Series, parallel and series-parallel. |
How many cells are there in a 24-volt lead-acid battery? | 12 |
What is the specific gravity of the electrolyte in a fully charged lead-acid battery? | Between 1.275 and 1.300. |
What is the range of temperatures of the electrolyte in a lead-acid battery that does not require that you apply a correction when measuring its specific gravity? | Between 70 degrees and 90 degrees Fahrenheit. |
What instrument is used to measure the specific gravity of the electrolyte in a lead-acid battery? | A hydrometer. |
How is a lead-acid battery compartment treated to protect it from corrosion? | Paint it with an asphaltic (tar base) paint or with polyurethane enamel. |
What is used to neutralize spilled electrolyte from a lead-acid battery? | A solution of bicarbonate of soda and water. |
How high should the electrolyte level be in a properly serviced lead-acid battery? | Only up to the level of the indicator in the cell. |
What precautions should be taken in a maintenance shop where both lead-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. |
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. |
What is used to neutralize spilled electrolyte from a nickel-cadmium battery? | A solution of boric acid and water. |
What is meant by electromagnetic induction? | The transfer of electrical energy from one conductor to another that is not electrically connected |
How many ohms are in a megohm? | One million (1,000,000). |
What part of an amp is a milliamp? | One thousandth (0.001). |