DC Sources of Electricity Flashcards
What is a primary cell?
What is a primary cell?
Can primary cells be recharged?
No, primary cells cannot be recharged and therefore cannot be reused, although they can and should be recycled.
What type of electrolyte is used in nearly all primary cells?
Nearly all primary cells use a paste electrolyte, making them dry cells.
Nearly all primary cells use a paste electrolyte, making them dry cells.
Zinc-carbon dry cells have a nominal initial voltage of about 1.5 V.
What are the main components of a zinc-carbon dry cell?
A zinc-carbon dry cell consists of a zinc container (negative electrode), a carbon rod (positive electrode), and a paste containing manganese (IV) oxide, zinc chloride, ammonium chloride, carbon powder, and water.
What is a disadvantage of zinc-carbon batteries?
As the zinc container oxidizes, it can eventually leak, so these batteries should only be installed in devices that are in use and not stored for extended periods.
How do alkaline primary batteries compare to zinc-carbon dry cells?
Alkaline batteries can deliver up to five times the energy of similarly-sized zinc-carbon batteries.
What can happen if you try to recharge an alkaline battery that is not designed to be recharged?
Attempting to recharge an alkaline battery not designed for recharging can cause the battery to rupture, leading to leakage of the potassium hydroxide electrolyte.
How are aircraft storage batteries composed?
Aircraft storage batteries are made of lead acid or nickel-cadmium cells connected in series within the battery case.
What distinguishes secondary cells from primary cells?
The electrochemical reactions in secondary (rechargeable) cells are reversible, allowing the chemical reactants to be restored by running a charging current into the cell.
Where are secondary cells commonly used?
Secondary cells are used in aircraft, cars, laptops, and many other devices.
How is battery capacity rated?
Battery capacity is rated in ampere-hours (Ah). For example, a battery with a capacity of 50 Ah can supply a current of 5 A for 10 hours.
What is the voltage of a fully charged lead acid cell?
A fully charged lead acid cell has a voltage of 2.2 V.
What happens during the discharge of a lead acid cell?
During discharge, sulfuric acid breaks up into hydrogen and sulfate ions. The sulfate ions combine with the negative lead plate to form lead sulfate, while hydrogen ions combine with the positive plate’s oxygen to form water, creating a flow of electrons from the negative to the positive plate.
What are the main components of a lead acid cell?
A lead acid cell consists of positive plates filled with lead peroxide (PbO2), negative plates filled with pure spongy lead (Pb), and an electrolyte made up of 30% sulfuric acid and 70% distilled water.
What happens during the charging of a lead acid cell?
During charging, sulfate ions are driven back into the electrolyte, forming sulfuric acid, and the plates return to their original composition of lead peroxide and spongy lead.
What is the voltage of a fully charged nickel cadmium cell?
A fully charged nickel cadmium cell has a voltage of 1.2 V.
What are the main components of a nickel cadmium cell?
A nickel cadmium cell consists of positive plates impregnated with nickel oxyhydroxide, negative plates made of metallic cadmium, and an electrolyte of potassium hydroxide.
What happens during the discharge of a nickel cadmium cell?
During discharge, hydrogen ions from the electrolyte combine with the negative plates, forming cadmium hydroxide, while hydroxide ions from the positive plates move into the electrolyte, creating a flow of electrons from the positive to the negative plate.
When should the electrolyte level of a nickel cadmium battery be checked and refilled?
The electrolyte level should be checked and refilled when the battery is fully charged, as the level rises during charging.
What are some advantages of nickel cadmium batteries compared to lead acid batteries?
Advantages of nickel cadmium batteries include higher discharge current tolerance, constant closed circuit voltage during discharge, higher energy density, and a greater number of charge/discharge cycles.
What are some disadvantages of nickel cadmium batteries compared to lead acid batteries?
Disadvantages of nickel cadmium batteries include higher cost, more complicated charging requirements, risk of thermal runaway, and high toxicity of cadmium.
What are the common types of primary coin cells and their uses?
Common types of primary coin cells include mercury oxide cells (used in hearing aids, watches, meters, and cameras), silver oxide cells (used in watches, calculators, and hearing aids), and lithium coin cells (used in pacemakers, cameras, and video cameras).
What are the key characteristics of mercury oxide coin cells?
Mercury oxide coin cells have a rated voltage of 1.35 V, constant internal resistance during discharge, and constant voltage even under continuous operation.
