What is the most important law applicable to the study of electricity?
Ohm’s Law (E = I x R)
What are the elements of Ohm’s Law?
Voltage (E), Current (I), and Resistance (R)
What are four sources of electrical energy?
Thermal, light, pressure, and chemical
What does an electrical circuit consist of?
- A source (Battery).
- Resistance or load (Light bulb)
- Conductors (Wires)
What represents capacitance in an AC circuit?
A capacitor (Same as a Condenser)
What is the function of a capacitor?
To store electricity
What is the unit of measure for a capacitance?
What is the standard unit of measure for frequency?
What is the basic component that only allows current to flow in one direction?
A diode (acts like a check valve)
What is inductance?
When voltage is induced by a 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.
What is an example of an inductor in a magneto?
What is impedance?
The total opposition for AC to flow caused by the combined effect of resistance, inductive reactance, and capacitive reactance in an AC circuit (Total resistance)
What causes opposition to the flow of current in AC circuit?
Inductive, and capacitance reactance.
What is the unit of measure for impedance?
What is the general purpose of a resistor?
To limit current.
how may the value of a small, fixed resistor be determined?
By the color bands on the resistor.
What are two things that happen when current flows through a conductor?
A magnetic field is generated, and the conductor heats up.
What is the common name for the lines of force that make up a field surrounding magnet?
Magnetic flux lines.
What is the concept that describes the relationship between electricity and magnetism?
What are the four factors that affect the resistance of an electrical conductor?
The wire gauge, length, temperature, and material.
What is the unit of measurement of power in a DC circuit?
The watt. Amperes times volts equals watts (P = I x E). 746 watts equals one horsepower.
What is a kilowatt?
it is 1,000 watts.
In a DC circuit, what occurs when voltage is increased while resistance remains constant?
There will be an increase in current.
What are the three types of DC electrical circuits?
They are Series circuits, Parallel circuits, and Complex circuits (Series and Parallel)
A 24-volt lead-acid battery has how many cells?
It has 12 cells and each cell is rated at approx. 2 volts.
What are the units that a battery capacity is measured in?
What should be the specific gravity of the electrolyte in a fully charged lead acid battery?
It should be between 1.275 and 1.300.
What instrument is used to determine the specific gravity of electrolyte in a lead acid battery?
Why can a hydrometer NOT be used to determine the charge of nickel-cadmium battery?
The specific gravity of the electrolyte in a nickel-cadmium battery does not change appreciably during charge or discharge or the battery?
When using a hydrometer to check the charge of a lead-acid battery, at what temperatures must correction factor be applied to the reading?
Adjustments must be made if temperature of the electrolyte is above 90F or below 70F.
What is electromagnetic induction?
It is the transfer of electrical energy by means of a magnetic field (lines of flux). Transferring voltage from one conductor to another without physically touching. This is the principle of transformer operation.
How are battery compartments protected against corrosion?
They are coated with a special corrosion resistant paint such as bituminous paint.
What should be the correct electrolyte level in a properly serviced battery?
It should be approximately 3/8 inches above the plates. If the battery has baffle plates above the cell plates, the electrolyte level should be up to the hole in the baffle plate in each cell.
What are paralleling generators and how is the load distributed?
This is when two or more generators are operated at the same time to supply power for a load that must be shared equally.
Describe a no-trip circuit breaker (trip free)
A “Trip Free” breaker makes it impossible to manually hold the circuit closed when excessive current is flowing. (It pops when a circuit gets hot and can’t be reset until it has cooled off.)
Can you store Ni-cad and Lead-acid batteries together?
No, the fumes from the Lead-acid battery can contaminate the electrolyte in the Ni-cad battery.
What is the result of an imbalanced cell in a nickel-cadmium battery?
When a cell has a low internal resistance, the current will increase across the cell, causing it to heat up.
What happens to the specific gravity of the electrolyte in a lead-acid battery when the temperature changes?
The specific gravity readings on a hydrometer will vary with the temperature variations. For example, as the temperature of the electrolyte increases, the specific gravity reading will be high, and colder electrolytes will have a lower apparent reading.
What is an L.E.D.?
Light Emitting Diode
What is an S.L.A.?
Sealed Lead-Acid Battery
What is the basic unit of measure for inductance?
What prevents reverse current flow in the D.C. Alternator?
Reverse current cutout.
How many wires may be installed on a single terminal lug>
How do you identify wire types?
Lettering on the insulation.
What is the maximum number of terminals that can be attached to a terminal strip stud?
No more than 4 terminal lugs for three terminal lugs and a bus bar should be connected to any one stud.