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Pre-Employment Electrician Theory > Cells And Batteries 030103b > Flashcards

Cells And Batteries 030103b Flashcards

1
Q

A device that changes chemical energy into electrical energy is called?

A

A cell.

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2
Q

What is the main difference between a primary cell and a secondary cell?

A

Primary cells are non-rechargeable
Secondary cells are rechargeable.

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3
Q

What does a basic cell consist of?

A

Electrodes that are immersed in an electrolyte within a glass, metal or plastic container.

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4
Q

What effects the voltage produced by a cell?

A

Type of materials used for the electrodes and the type of electrolyte.

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5
Q

What two basic factors affect the capacity of a cell?

Objective 1 Page 3

A

The area and mass of the electrodes.

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6
Q

What are the two basic types of cells?

Objective 1 Page 2

A

Primary

Secondary.

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7
Q

Why is the Leclanche cell referred to as a dry cell?

Objective 2 Page 6

A

The electrolyte is a paste made of zinc chloride and ammonium chloride instead of a liquid.

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8
Q

What type of cell is a lead-acid cell?

Objecive 3 Page 9

A

Secondary

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9
Q

What are the three main types of lead-acid batteries?

Objective 3 Page 9

A

Flooded Cell

Gelled Electrolyte Cell

Absorptive Glass Mat (AGM) Cell

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10
Q

What type of lead-acid battery is the most common?

Objective 3 Page 9

A

Flooded Cell

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11
Q

What is the main difference between flooded cell and other lead-acid batteries?

Objective 3 Page 9

A

The electrolyte is liquid.

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12
Q

What type of lead-acid battery is used extensively as an automotive battery?

Objective 3 Page 9

A

Flooded cell.

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13
Q

What is a hydrometer for?

Objective 3 Page 10

A

Is an instrument used for measuring density of liquids. Can be used to test the gravity in batteries.

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14
Q

What is the open circuit voltage in a fully charged lead-acid cell?

Objective 3 Page 11

A

2.1 V per cell.

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15
Q

What terminal voltage should lead-acid batteries not be allowed to drop below to avoid permanent damage?

Objective 3 Page 11

A

1.75 V per cell.

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16
Q

What type of batteries can Gelled electrolyte cell and Absorptive Glass Mat (AGM) cell batteries referred to as?

Objective 3 Page 13

A

Valve-regulated lead-acid (VRLA)

They have one way valves that release gas pressure if the battery is recharged incorrectly.

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17
Q

The electrolyte used in a lead-acid cell is a dilute solution of what?

Objective 3 Page 10

A

Sulphuric Acid.

18
Q

In a fully charged lead-acid cell, what is the specific gravity of the electrolyte?

Objective 3 Page 11

A

Between 1.25 and 1.28

19
Q

What are the three advantages of using a gelled electrolyte battery instead of a lead-acid battery?

Objective 3 Page 12

A

Maintenance Free

Does not spill or leak (Corrosion Resistant)

Has no hazardous gas accumulations.

20
Q

What is the open circuit voltage of a Ni-Cad cell?

Objective 4 Page 15

A

1.2V per cell.

21
Q

How many cells does a 12 V Ni-Cad battery have?

Objective 4 Page 15

A

10 cells.

22
Q

What are the 7 advantages of using a Ni-Cad battery over a lead-acid battery?

Objective 4 Page 15

A

Higher energy to weight ratio.

Lower internal resistance.

Faster recharge rates.

Longer storage life.

Operate reliably at higher or lower temperatures.

Capable of complete discharge/recharge.

Vented type rarely need water added.

23
Q

What are some common applications for Ni-Cad batteries?

Objective 4 Page 16

A

Rechargeable tools, laptop computers and cameras.

Uninterruptible Power Supply (UPS) and emergency lighting.

Energy storage devices.

Utility Backup Power.

24
Q

How much voltage can a lithium battery produce?

Objective 5 Page 18

A

3 to 3.7 V

25
Q

What are some advantages of lithium batteries?

Objective 5 Page 20

A

Very lightweight.

Very high energy density.

Hold their charge. Loses only about 5% per month.

No memory. Can recharge at any time.

Can be charged and discharged hundreds of times.

26
Q

What are some disadvantages of lithium batteries?

Objective 5 Page 21

A

Only last 2-3 years from date of manufacture.

Very sensitive to high temperatures.

Complete discharge destroys it.

Must be monitored by an on-board computer.

Can burst into flame when they fail.

Expensive.

27
Q

What must be done to recharge a cell or battery?

Objective 6 Page 23

A

A voltage must be applied to have current flow in the reverse direction.

28
Q

Why should cells have the same current when they are being recharged?

Objective 6 Page 24

A

To avoid cells from being overcharged.

29
Q

What can happen if the cell temperature becomes excessively high during charging?

Objective 6 Page 23

A

Plate structure may be damaged and excessive gassing occurs.

30
Q

What can happen if a fully charged battery is connected in parallel with a dead battery?

Objective 6 Page 24

A

Excessive gassing can occur and cause one battery to explode.

31
Q

What do discharged lead-acid batteries tend to freeze in cold weather?

Objective 6 Page 24

A

The electrolyte solution dilutes and becomes more like water.

32
Q

What kind of gas is produced when charging batteries?

Objective 6 Page 24

A

Hydrogen gas.

33
Q

What does an ampere-hour rating (A*h) indicate?

Objective 7 Page 26

A

Total energy capacity of a battery. Current multiplied by time.

34
Q

What percentage must the terminal voltage not fall below at the end of the ampere-hour rating time?

Objective 7 Page 26

A

91%

35
Q

How long must a battery be able to provide power to the lights for?

Objective 7 Page 26

A

At least 30 mins.

36
Q

What does the cranking amps (CA) rating indicate?

Objective 7 Page 26

A

Indicates the current that can be drawn from a fully charged battery for 30 secs at a temp of 0℃ without cell voltage falling below 1.2 V per cell.

37
Q

What does the cold cranking amps (CCA) rating indicate?

Objective 7 Page 26

A

Indicates the current that can be drawn from a fully charged battery for 30 secs at a temp of 0°F without cell voltage falling below 1.2 V per cell.

38
Q

What does the reserve capacity rating indicate and what is it quoted in?

Objective 7 Page 27

A

Indicates the number of minutes a fully charged lead-acid battery can maintain 25A at 25℃ before the voltage drops below 1.75 V per cell.

Quoted in minutes.

39
Q

What unit of measurement is used when the cold cranking performance rating is given?

Objective 7 Page 26

A

Amperes.

40
Q

Is internal resistance considered to be in series or in parallel with the cell?

Objective 8 Page 29

A

In series.

41
Q

How do you calculate the volt drop of the internal resistance of a cell?

Objective 8 Page 29

A

The difference between the open circuit terminal voltage and the voltage under load conditions.
Vno load - Vwith load = Vdrop due to internal resistance.

Pre-Employment Electrician Theory (8 decks)

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