Subject A - Basic Electricity

Question 1

What is the most important law applicable to the study of electricity (ohm’s law equation)?

Answer 1

Ohm’s Law (E = I x R).

Question 2

What are the elements of Ohm’s Law?

Answer 2

Voltage (E), Current (l), and Resistance (R).

Question 3

What are four sources of electrical energy?

Answer 3

Thermal, light, pressure, chemical, and magnetic.

Question 4

What does an electrical circuit consist of?

Answer 4

1. A source (battery). 2. Resistance or load (Light bulb). 3. Conductors (Wires).

Question 5

What represents capacitance in an AC circuit?

Answer 5

A capacitor (same as a condenser).

Question 6

What is the function of a capacitor?

Answer 6

To store electricity.

Question 7

What is the unit of measure for capacitance?

Answer 7

Farad.

Question 8

What is the standard unit of measure for frequency?

Answer 8

Hertz.

Question 9

What is the basic component that only allows current to flow in one direction?

Answer 9

A diode (acts like a check-valve).

Question 10

What is inductance?

Answer 10

Induced voltage which is opposite in direction to the applied voltage.

Question 11

What is an example of an inductor in a magneto?

Answer 11

The coil.

Question 12

What is impedance (define the term impedance)?

Answer 12

The total opposition to the flow of current in an electrical circuit.

Question 13

What causes opposition to the flow of current in an AC circuit?

Answer 13

Resistance, Inductive, and capacitance reactance.

Question 14

What is the unit of measurement for impedance?

Answer 14

Ohms.

Question 15

What is the general purpose of a resistor?

Answer 15

To limit current.

Question 16

How may the value of a small, fixed resistor be determined?

Answer 16

By the color bands on the resistor.

Question 17

What are two things that happen when current flows through a conductor?

Answer 17

A magnetic field is generated, and the conductor heats up.

Question 18

What is the common name for the lines of force that make up a field surrounding a magnet?

Answer 18

Magnetic flux lines.

Question 19

What is the concept that describes the relationship between electricity and magnetism?

Answer 19

Electromagnetism.

Question 20

What are the four factors that affect the resistance of an electrical conductor?

Answer 20

The wire gauge, length, temperature, and material.

Question 21

What is the unit of measurement of power in a DC circuit?

Answer 21

The watt. Amperes times volts equals watts (P = I x E). 746 watts equals one horsepower.

Question 22

What is a kilowatt?

Answer 22

It is 1,000 watts.

Question 23

In a DC circuit, what occurs when voltage is increased while resistance remains constant?

Answer 23

There will be an increase in current.

Question 24

What are the three types of DC electrical circuits?

Answer 24

They are Series circuits, Parallel circuits, and complex circuits (series and parallel).

Question 25

A 24 volt lead-acid battery has how many cells?

Answer 25

It has 12 cells. Each cell is rated at approx. 2 volts. 12 C x 2 V = 24V

Question 26

What are the units that battery capacity are measured in?

Answer 26

Ampere-hours.

Question 27

What should be the specific gravity of the electrolyte in a fully charged lead acid battery?

Answer 27

It should be between 1.275 and 1.300.

Question 28

What instrument is used to determine the specific gravity of electrolyte in a lead acid battery?

Answer 28

A hydrometer.

Question 29

Why can a hydrometer NOT be used to determine the charge of a nickel-cadmium battery?

Answer 29

The specific gravity of the electrolyte in a nickel-cadmium battery does not change appreciably (enough to be notice) during charge or discharge of the battery.

Question 30

When using a hydrometer to check the charge of a lead-acid battery, at what temperatures must a correction factor be applied to the reading?

Answer 30

Adjustments must be made if temperature of the electrolyte is above 90°F or below 70°F. 80 F don’t require temperature corrections.

Question 31

What is electromagnetic induction?

Answer 31

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.

Question 32

How are battery compartments protected against corrosion?

Answer 32

They are coated with special corrosion resistant paint such as bituminous paint.

Question 33

What should be the correct electrolyte level in a properly serviced battery?

Answer 33

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.

Question 34

What are paralleling generators and how is the load distributed?

Answer 34

when two or more generators are operated at the same time to supply power for a load that must be shared equally.

Question 35

Describe a no-trip circuit breaker (trip free).

Answer 35

A "Trip Free" breaker makes it impossible to manually hold the circuit closed when excessive current is flowing. (It pops when circuit gets hot and can't be reset until it has cooled off.)

Question 36

Can you store Ni-cad and Lead-acid batteries together?

Answer 36

No, the fumes from the Lead-acid battery can contaminate the electrolyte in the Ni-cad battery.

Question 37

What is the result of an imbalanced cell in a nickel-cadmium battery?

Answer 37

When a cell has a low internal resistance, the current will increase across the cell, causing it to heat up.

Question 38

What happens to the specific gravity of the electrolyte in a lead acid battery when the temperature changes?

Answer 38

The specific gravity readings on a hydrometer will vary with temperature variations.

Question 39

What is the difference between permanent and temporary magnets?

Answer 39

When an external magnetizing force is removed, permanent magnets retain their magnetism for an extended time whereas temporary magnets quickly lose most of their magnetism.

Question 40

What is one of the most frequent cause of damage to solid-state components and integrated circuits?

Answer 40

Electro-static discharge (ESD) from the human body due to careless handling.

Question 41

In regards to batteries, what is an SLA battery?

Answer 41

Sealed Lead Acid battery.

Question 42

How would a technician connect a meter in a circuit to read it's current?

Answer 42

Insert the meter in series by opening or breaking the circuit.

Question 43

What is one advantage of a.c. circuits over d.c. circuits in aircraft?

Answer 43

AC can be transmitted over long distances more readily and more economically than DC; 2) Space and weight can be saved; 3) Circuit breakers will operate satisfactorily at altitude; 4) AC devices are smaller and simpler; or 5) Most 24-volt aircraft systems have special equipment that requires a certain amount of 400 cycle AC current.

Question 44

What is the basic unit of the measure of inductance?

Answer 44

Henry.

Question 45

What component can change the electrical energy of a voltage to a different level of energy?

Answer 45

Transformer.

Question 46

What does the acronym LED stand for?

Answer 46

Light Emitting Diode.

Question 47

Describe a basic AND gate.

Answer 47

A standard logic symbol that has two inputs or more and one output. the two input signals must be received (true) in order for there to be an output signal transmitted.

Question 48

When using a multi-meter what setting, or type of check, is typically used to determine an open in a conductor?

Answer 48

Continuity.

Question 49

What component can transform Alternating Current into Direct Current?

Answer 49

A Rectifier.

Question 50

Name the two types of batteries commonly used in modern aircraft.

Answer 50

Lead Acid, and Nickel Cadmium.

Question 51

Why is a specific gravity check of the electrolyte in a nickel-cadmium batter not acceptable to determine battery charge?

Answer 51

The electrolyte special gravity does not change with the state of charge.

Question 52

What are two reasons that might cause a nickle-cadmium battery to fail to delivery its rated capacity?

Answer 52

Faulty cells and cell imbalance.