Electricity Oral 3

Question 1

What is meant by the capacity rating of a lead-acid battery?

Answer 1

The number of hours a battery can supply a given current flow.

Question 2

What electrolyte is used in a lead-acid battery?

Answer 2

A mixture of sulfuric acid and water.

Question 3

What is the specific gravity of a fully charged lead-acid battery?

Answer 3

Between 1.275 and 1.300.

Question 4

What is the range of temperature of the electrolyte in a lead-acid battery that does not require a correction when measuring its specific gravity?

Answer 4

Between 70 and 90 degrees Fahrenheit.

Question 5

How do you treat a lead-acid battery compartment to protect it from corrosion?

Answer 5

Paint it with an asphaltic (tar base) paint or with a polyurethane enamel.

Question 6

How high should the electrolyte level be in a properly serviced lead-acid battery?

Answer 6

Only up to the level of the indicator in the cell.

Question 7

What is the open-circuit voltage of a lead-acid cell?

Answer 7

2.1 volts

Question 8

What precautions should be taken in the maintenance shop where both lead-acid and nickel-cadmium batteries are being serviced?

Answer 8

The two types of batteries should be kept separate, and the tools used on one type should not be used on the other.

Question 9

Why is a hydrometer not used to measure the state of charge of a nickel-cadmium battery?

Answer 9

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.

Question 10

What is a result of cell imbalance in a nickel-cadmium battery?

Answer 10

The low internal resistance allows current to flow between the unbalanced cells and generate heat.

Question 11

How may thermal runaway be prevented?

Answer 11

By carefully monitoring the temperature of the middle cells and controlling the charging current to prevent an excess of current flowing into the battery.

Question 12

What is used to neutralize spilled electrolyte from a nickel-cadmium battery?

Answer 12

A solution of boric acid and water.

Question 13

In what units is battery capacity expressed?

Answer 13

In ampere-hours.

Question 14

Does the specific gravity of the electrolyte in a lead-acid battery increase or decrease as the battery becomes discharged?

Answer 14

It decreases.

Question 15

How many cells are there in a 24-volt lead acid battery?

Answer 15

12

Question 16

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

Answer 16

A hydrometer.

Question 17

What is used to neutralize spilled electrolyte from a lead-acid battery?

Answer 17

A solution of bicarbonate soda and water.

Question 18

Why is the closed-circuit voltage of a lead-acid battery lower than its open-circuit voltage?

Answer 18

Voltage is dropped across the internal resistance of the battery.

Question 19

What gases are released when a lead-acid battery is being charged?

Answer 19

Hydrogen and Oxygen.

Question 20

What is the electrolyte used in a nickel-cadmium battery?

Answer 20

Potassium hydroxide and water.

Question 21

Is the electrolyte level of a nickel-cadmium battery lowest when the battery is fully charged or fully discharged?

Answer 21

Fully discharged.

Question 22

What is a thermal runaway?

Answer 22

The large current flow allowed by the low internal resistance causes the middle cells to produce more heat than they can dissipate. The heat further lowers the internal resistance so more current can flow; this continues until the battery destroys itself.

Question 23

How is it possible to know when a nickel-cadmium battery is fully charged?

Answer 23

Completely discharge the battery and give it a constant-current charge to 140% of its ampere-hour capacity.