3.5 DC Sources Of Electricity

Question 1

In a primary cell is the electrochemical processes taking place reversible?

Answer 1

No

Question 2

Can primary cells immediately supply voltage without charging beforehand?

Answer 2

Yes

Question 3

Can primary cells be recharged or reused?

Answer 3

No but they can be recycled

Question 4

What is capacity of a battery?

Answer 4

The quantity of electricity

Question 5

1 ampere-hour is how many coulombs?

Answer 5

3,600 coulombs

Question 6

What determines a batteries capacity?

Answer 6

Their construction and size

Question 7

Most primary cells are wet or dry cells?

Answer 7

Dry cells

Question 8

Why should zinc-carbon batteries not be used in devices for extended periods of time?

Answer 8

The zinc container oxidises causing the contents to leak

Question 9

Is the electrochemical reaction in a secondary cell reversible?

Answer 9

Yes

Question 10

How can the chemical reactants be restored in a secondary cell?

Answer 10

By running a charging current through them

Question 11

In aircraft storage what are the secondary cell made from?

Answer 11

Lead acid or nickel cadmium

Question 12

How are the aircraft storage batteries connected?

Answer 12

In series within the battery case

Question 13

A group of cells connected together in series is called?

Answer 13

A battery of cells (abbreviated to ‘battery’)

Question 14

Lead acid cells have a charged voltage of?

Answer 14

2.2volts

Question 15

Lead acid cells have a final discharge voltage of?

Answer 15

1.83volts

Question 16

A lead acid cell consists of?

Answer 16

-positive lead peroxide plates
-negative pure sponges lead plates
-a liquid electrolyte (30%acid 70% water)

Question 17

When is a lead acid cell said to be discharged?

Answer 17

When the plates go through a chemical process and are coated in lead sulphate where no further chemical action takes place

Question 18

Nickel cadmium cells have a voltage of?

Answer 18

1.2 volts

Question 19

When a nickel cadmium cell is discharged what will the voltage fall to?

Answer 19

1.0 volts

Question 20

What are the components of a nickel cadmium cell?

Answer 20

-positive nickel oxyhydroxides plates
-negative metallic cadmium plates
-potassium hydroxide electrolyte

Question 21

When is the only time you should refill a nickel cadmium battery?

Answer 21

When its fully charged

Question 22

When is the electrolyte level in a nickel cadmium battery at its lowest?

Answer 22

After discharge

Question 23

How do you create a series of connections for batteries?

Answer 23

By connecting unlike terminals

Question 24

The series connection of power sources increases the?

Answer 24

Voltage

Question 25

What stays the same through a series circuit?

Answer 25

The current

Question 26

What happens to the internal resistance of the battery if its cells are connected in series?

Answer 26

It increases

Question 27

Why is it better to connect like owner sources. In parallel than in series?

Answer 27

It provides the same voltage but lowers the total internal resistance

Question 28

Why should you only connect like power sources in parallel instead of different power sources?

Answer 28

Because connecting different power sources can create an unintended circulating current

Question 29

A power source (battery) generates voltage, what is this also known as?

Answer 29

Source voltage

Question 30

Why is the total source voltage not available at the terminals?

Answer 30

Due to the internal resistance

Question 31

What is terminal voltage?

Answer 31

The amount of voltage you have at the terminals due to internal resistance

Question 32

What is the definition of a short circuit?

Answer 32

The terminals of the battery are directly connected to each other

Question 33

What is a short-circuit current?

Answer 33

When a battery has been short circuited and a high current flows in the circuit

Question 34

What is the short circuit current limited by?

Answer 34

The international resistance of the battery

Question 35

The total source voltage drops at the?

Answer 35

Internal resistance

Question 36

What happens if the short circuit currents are too high?

Answer 36

It will destroy the power source

Question 37

What increases as the battery discharges?

Answer 37

The internal resistance

Question 38

What is a thermocouple?

Answer 38

When two different metals are connected and heated to created a voltage

Question 39

What is the voltage from a thermocouple referred to as?

Answer 39

Thermoelectric voltage

Question 40

In aviation where are thermocouples mainly used?

Answer 40

To measure exhaust gas temperatures of engines

Question 41

In aviation what are the two main alloys used in a thermocouple?

Answer 41

Chrome and alumel

Question 42

How does a phot-cell work?

Answer 42

When exposed to light it releases electrons to generate a voltage (like a light sensor)

Question 43

What are photocells used for on an aircraft?

Answer 43

Automatic light level adjustment for the crew