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28 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is a cell |
Unit that contains a chemical reaction |
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What is a battery |
Group of cells |
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When dissimilar metals are brought into contact or connected together through a conductive medium to create electron transfer |
Elextrochemical (Galvanic) action |
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What is the role of the anode |
To supply electrons to an external circuit |
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What is the role of the cathode |
Accepts the electrons from an external circuit |
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What are the two battery types |
Primary and secondary |
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Characteristics of primary batteries |
Are not rechargeable. Once chemical inside is depleted the battery is unusable |
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Characteristics of secondary batteries |
Are rechargeable. Once chemical inside is depleted the chemical process can be reversed |
Phone battery work like this |
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How does a primary cell work |
It uses an electrochemical reaction created by the zinc case and manganese dioxide to produce voltage and current |
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What is the use of the carbon rod in the primary cell |
Only to conduct current |
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What batteries are used in aviation |
Led acid, nickel cadmium and lithium Ion |
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What is deionised water |
It's water where the ions have been removed to create pure water |
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What happens to a battery as it discharges |
The amount of water into the electrolyte increases so the acid become weaker |
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How do we measure the state of change in a lead acid battery |
By checking the specific gravity of the electrolyte. This is done using a hydrometer |
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Formula for specific gravity (SG) |
SG= Density of electrolyte/density of pure water |
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What is is called when individual cells share and equalise charge |
Constant voltage |
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Constant current is when |
some cells become fully charged before others and can become overcharged |
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How is a led acid battery charged |
By reversing the chemical reaction which occurs when the battery is being used. |
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What is lead sulphate |
It's discharge from the normal cycle of a battery which gets deposited and sometimes permanetly attached to the plates which can cause cell voltage to drop |
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How is sulphation made worse |
By continual trickle charge by incorrect electrolyte SG or lower electrolyte levels |
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Advantages of nickel cadmium (NiCad) batteries |
Longer life, lighter, less maintenance required and work better under cold temperatures |
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Disadvantages of NiCad batteries |
expensive, lower voltage per cell and are volotile |
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What is the memory affect |
Is the change in crystalline structure of the battery plates and can be caused by recharging the battery before it's properly discharged |
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How to prevent the memory affect |
By allowing the battery to properly discharge before charging |
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What is trickle charge |
Means charging a fully charged battery at the rate equal to its self discharge rate |
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How is a batteries capacity reduced |
By the secondary chemical reacting with the cell, damage caused by deep discharge and reduction of internal storage capacity |
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What is a capacity test |
Measure the time taken for the battery to reach its end voltage |
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How do we calculate the percentage capacity of a battery |
Time to end voltage/60mims×100% |
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