Energy Transfer in a Cricuit
Cells and batteries are useful sources of electricity.
Chemical energy to Electrical energy
There are two types of cells:
1.Primary cell
2.Secondary cell
Chemical energy to Electrical energy
There are two types of cells:
1.Primary cell
2.Secondary cell
Primary Cell
The dry cell is an example of a PRIMARY CELL. The reactions in a primary cell cannot be reversed (primary cells cannot be recharged). |
The dry cell contains a mixture of powdered carbon and manganese dioxide. The carbon improves conduction and the manganese dioxide reduces polarization.
Polarization is the process by which hydrogen atoms build up around the positive terminal of the cell.
Polarization reduces both the potential difference (p.d) and the current that the cell can provide.
Polarization is the process by which hydrogen atoms build up around the positive terminal of the cell.
Polarization reduces both the potential difference (p.d) and the current that the cell can provide.
ZINC-CARBON DRY CELL
emf 1.5V Internal Resistance 0.5Ω Maximum Current About 1A Advantages Small Portable Disadvantages Not rechargeable Can leak if stored or used Depolariser Manganese Dioxide |
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Secondary Cell
Example: A lead-acid battery
Negative Electrode
Grey lead plate
Positive Electrode
Brown lead (IV) oxide [PbO2]
Electrolyte
Dilute Sulphuric Acid
emf
12V
Internal Resistance
0.01Ω
Maximum Current
400A
Advantages
Rechargeable
Can supply a very large current
Disadvantages
Heavy and bulky
Needs topping up with distilled water
Grey lead plate
Positive Electrode
Brown lead (IV) oxide [PbO2]
Electrolyte
Dilute Sulphuric Acid
emf
12V
Internal Resistance
0.01Ω
Maximum Current
400A
Advantages
Rechargeable
Can supply a very large current
Disadvantages
Heavy and bulky
Needs topping up with distilled water