Credit: Anton Fomkin
License: CC BY-NC 3.0
Creating electrical energy via stored chemical energy, batteries are able to power the millions of devices that surround us every day.
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- A battery is a group of chemical cells where each cell consists of two metal plates, or electrodes, that are immersed in a conducting fluid. Due to a chemical reaction between the plates and the fluid, one of the plates becomes more positively charged than the other. Usually considered as ideal batteries, ideal batteries are a source of an electromotive force (emf) that is able to maintain a constant potential difference between the two terminals.
- All real batteries have an internal resistance, meaning the potential difference between the terminals is not the same as the electromotive force of the battery. In a real battery, there exists an internal resistance of the battery given by r. By creating a circuit diagram of a battery, it is easy to see that the voltage across the terminal in a real battery is given as:
Using the information provided above, answer the following questions.
- A 9 Ω resistor is connected across a battery of emf 5 V and internal resistance of 1 Ω. What is the current?
- If the emf of the battery is doubled, what would the current be in the previous problem?
- Is the terminal voltage greater or less than the emf of the battery?