3.5(2) DC Theory

Question 1

Chemical energy converted to electrical energy is known as?

Answer 1

electrochemical action

Question 2

What will vary the voltage across the electrodes of a cell?

Answer 2

The material the electrodes are made of and the composition of the electrolyte.

Question 3

What factors effect the internal resistance of a cell?

Answer 3

size of the electrodes and the distance between them.

Question 4

How can you lower internal resistance of a cell?

Answer 4

by making the electrodes larger or bringing them closer together.

Question 5

How are secondary cells able to be recharged?

Answer 5

chemical action which produces the electric current can be reversed returning the cell to the charged condition.

Question 6

What happens to the electrodes in a primary cell?

Answer 6

Chemical action eats away one of the electrodes usually the negative electrode., causing it to be replaced.

Question 7

What are the 4 basic types of wet cells?

Answer 7

Lead acid, mickel cadmium, silver zinc, silver cadmium

Question 8

In a secondary cell the electrodes and electrolyte are altered when

Answer 8

the cell delivers current, these cells may be restored to original condition by forcing current through them in the opposite direction of discharge.

Question 9

What type of materials are used in alead acid battery?

Answer 9

Positive plates = lead peroxide, negative plates = pure spongy lead, electrolyte = sulfuric acid and water.

Question 10

What is the V of a open circuit (no load) lead acid CELL

Answer 10

2V

Question 11

In a battery there is always one more plate of which polarity?

Answer 11

There is always one more negative plate then positive plate.

Question 12

What is the purpose of the seperators between the plates of a bettery?

Answer 12

Hold the plates apart while allowing free movement of the ELECTROLYTE!

Question 13

How are the plates connected internally of the battery?

Answer 13

In series by link connectors, one end of the positive plates will act as the terminal, one end of the negative plates will act as the other negative terminal.

Question 14

In a lead acid battery if a cell fails what must be done?

Answer 14

The battery must be replaced.

Question 15

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

Answer 15

1.270 twelve seventy

Question 16

When will electron flow stop and the battery be discharged?

Answer 16

When both plates are converted to lead sulfate no further chemical action is possible.

Question 17

During battery discharge what happens to the negatively charged sulfate ions?

Answer 17

Negatively charged sulfat ions combine with the lead in the plates and form LEAD SULFATE., giving up their charge creating an EXCESS of electrons on the negative plate.

Question 18

During discharge what happens to the hydrogen ions?

Answer 18

Hydrogen ions go to the positive plate and combine with oxygen of the LEAD PEROXIDE forming water, stealing electrons from the positive plate forming LEAD SULFATE on positive plate.

Question 19

When the discharging battery is connected to a load what happens to the electrons?

Answer 19

Positive plate ends up with a defficiency of electrons, while the negative plate has an excess. forcing the electrons around the circuit from negative to positive.

Question 20

How is a battery charged?

Answer 20

Current flow is reversed, sulfate ions are driven back into the solution off the electrodes, the plates return to original composition of spongy lead (-) and lead peroxcide (+).

Question 21

What materials are used in the Nicad Battery?

Answer 21

Positive = Nickel hydroxide, Negative = cadmium hydroxide, Electrolyte = Potassium hydroxide (Discharged state)

Question 22

What is an advantage of the nickel cadmium battery?

Answer 22

It can stand in the discharged state with little to none detioration.

Question 23

What is the SG of a Nicad battery?

Answer 23

About 1.300

Question 24

What are some advantages o the nicad battery?q

Answer 24

Charged in shorter time, stay ide longer in any state of charge, be charged and discharged any number of times.

Question 25

What is the open circuit (no-load) cell voltage for a nicad?

Answer 25

1.3V

Question 26

How is thermal runaway indicated?

Answer 26

Battery charging current rises instead of falling as the charge progresses., high temperature lowers internal resistance causing excessive current draw.

Question 27

What are the materials of a silver zinc cell?

Answer 27

Positive = Silver oxide, Negative terminal = zinc, electrolyte = potassium hydroxide.

Question 28

Advantages of a silver zinc cell?

Answer 28

High out put, ideal for miniture devices.

Question 29

Cells connected in series =?

Answer 29

Higher Voltage

Question 30

Cells connected in parallel?

Answer 30

Higher current

Question 31

What is a disadvantage to batteries connected in series?

Answer 31

The internal resistance of the batteries add up lowering the current supply capability for the circuit.

Question 32

Explain batteries connected in parallel.

Answer 32

Voltage will stay the same but total current output increases. if one cell shorts the entire system fails as all cells will discharge through the shorted circuit.

Question 33

How is the Potential difference (Voltage) measured on a thermocouple?

Answer 33

Measured at the cold junction between the 2 dissimilar metals.

Question 34

Generating potential difference via heat is named.

Answer 34

Seebeck effect. (10mV)

Question 35

Thermo couple type T?

Answer 35

Copper Constantan upto 400c

Question 36

Thermocouple type J?

Answer 36

Iron constantan - range upto 850C

Question 37

Thermo couple type K

Answer 37

Chromel alumel - range upto 1200C

Question 38

What type of material are photovoltaic cells made up?

Answer 38

Semiconducting materials, N type and P type silicon