Cells, EMF, Internal Resistance | Physics

Luigi Galvani an Italian scientist, while cutting a frog’s leg his steel scalpel touched against one of the frog’s nerves and the leg muscles jerked. The leg twitched. He called this Phenomenon as animal electricity. Copy the link given below and paste it in new browser window to get more information on Cells, EMF, Internal Resistance www.askiitians.com/iit-jee-electric-current/cells-emf-internal-resistance/

1. Cells, EMF, Internal resistance

2. Contents History Cell or battery Primary cell and secondary cell EMF and internal resistance

3. History Alessandro Volta invented electric battery known as Voltaic pile. John Frederic Daniell - developed Daniell cell. George Leclanche invented Wet cell. Dr. Carl Gassner introduced the Dry cell battery. Gaston Plante introduced the first rechargeable battery.

4. Cell or battery A cell consists of three parts. Electrodes - A positive terminal and negative terminal. Electrolyte- a chemical solution. A combination of two or more cells is called battery. When chemical reaction takes place reduction reaction occurs at cathode and oxidation process occurs at anode .

5. A cell

6. Primary cell and secondary cell A primary cell is not able to charge again and so it can be used only once. It is possible to charge again in a secondary cell and thus it can be reused again and again Cells can be connected both in series and parallel. .

7. Batteries at home It is possible to make batteries at home using potato, lemon etc. Potato act as an electrolyte.

8. Emf and internal resistance Electromotive force is the potential difference developed between the two terminals of a battery in an open circuit. ε = E/Q, where ε is the electromotive force, E is the energy and Q is the charge. Internal resistance within the battery resists the current flow when connected to a circuit and causes a voltage drop when current flows through it. V = ε – Ir , where V is the potential difference across the circuit, ε is the emf, I is the current flowing through the circuit, r is internal resistance.

9. Emf and internal resistance

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