Basic Electricity

Question 1

What is the most important law applicable to the study of electricity?

Answer 1

Ohm’s Law (E=IR) (Voltage = AmpsResistance)

Question 2

What are the elements of Ohm’s Law?

Answer 2

Voltage (E), current (I), and resistance (R).

Question 3

What are the sources of electrical power?

Answer 3

Mechanical (generator), chemical (battery), photoelectric (light), and thermal (heat).

Question 4

What does an electrical circuit consist of?

Answer 4

A source of electrical pressure or EMF, resistance in the form of an energy consuming electrical device,
and conductors, usually in the form of copper or aluminum wires, to provide a path for electron flow.

Question 5

What represents capacitance in an AC circuit?

Answer 5

A capacitor (condenser).

Question 6

What is the function of a capacitor?

Answer 6

To store electricity.

Question 7

What is inductance?

Answer 7

A voltage that is induced in a coil in an AC circuit. This voltage is opposite in direction to the applied
voltage, and opposes any change in the alternating current.

Question 8

What is impedance?

Answer 8

It is the combined effect of resistance, inductive reactance, and capacitive reactance in an AC circuit.

Question 9

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

Answer 9

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

Question 10

What is a kilowatt?

Answer 10

It is 1,000 watts.

Question 11

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

Answer 11

There will be an increase in current.

Question 12

What are the three types of DC electrical circuits?

Answer 12

They are series circuits, parallel circuits, and series-parallel circuits.

Question 13

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

Answer 13

It has 12 cells. Each cell is rated at 2 volts.

Question 14

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

Answer 14

It should be between 1.275 and 1.300

Question 15

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

Answer 15

Hydrometer

Question 16

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

Answer 16

The specific gravity of the electrolyte in a nickel-cadmium battery does not change appreciably during
charge or discharge of the battery.

Question 17

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 17

Adjustments must be made if temperature of the electrolyte is above 90° F or below 70°F

Question 18

What is electromagnetic induction?

Answer 18

It is the transfer of electrical energy by means of a magnetic field. This is the principle of transformer
operation.

Question 19

How are battery compartments protected against corrosion?

Answer 19

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

Question 20

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

Answer 20

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 21

Why should nickel-cadmium batteries and lead-acid batteries not be stored or serviced in the same area?

Answer 21

The electrolyte in nickel-cadmium batteries is chemically opposite to the lead-acid battery electrolyte and
the fumes from lead-acid battery can contaminate the electrolyte in the nickel-cadmium batteries.