Oral Questions-basic Electricity Flashcards
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 states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant.
What are the three elements in ohms law?
Voltage, current, and resistance. (Volts, amps, ohms.)
What are five sources of electrical energy?
Magnesium, chemical energy, light, heat and pressure.
What are four things affect the resistance of an electrical conductor?
The material, the cross-sectional area, the length and the temperature.
How can your 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 elecrtrolytic capacitor will pass current of one 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 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 kilo watt?
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 temperature of the electrolyte in a lead-acid battery 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 property 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 be used on the other.
Why is a hydrometer not used to measure the state of charge of 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 mag ohm?
One million.
What part of an amp is a milliamp?
One thousandth 0.001.
