Work, Energy and Power  

When a real battery of emf E and internal resistance r does work on the charge carriers in a current i through it, the rate P of energy transfer to the charge carriers is:

                                                               P = iV                                     

Where V is the potential across the terminals of the battery. The rate P_therm of energy transfer to thermal energy within the battery is given by:

                                                                                                           P_therm = i²r  

The rate P_emf at which the chemical energy within the battery changes is given by:

                                                                                                              P_emf  =  iE                                 

Where the relationship between the resistance R, internal resistance r and current in a circuit is given by: 

                                                                                                           (E   - ir)  =  iR  
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Quiz 

If the potential difference across a light bulb is 10V and the resistance of the bulb is 5 Ohms, then the energy dissipated by the bulb is equal to:


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