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Home Minds On Electric Circuits Mission EC2 Voltage Help Help 7

Mission EC2 Voltage

The Question

Which one of the following is true about the electrical circuit in your flashlight?

Physics Rules

The Role of a Battery:
The role of a battery (or cell) in an electric circuit is to supply energy to the circuit by doing work upon the charge to move it from the low energy terminal to the high energy terminal. By moving charge to high energy, the battery (or cell) is establishing a difference in electric potential across the two ends of the external circuit. With this difference in electric potential established, charge will spontaneously flow through the external circuit.

Think About It

In a sense, circuits are all about energy. Energy is introduced into the circuit by the battery. The battery acts as a charge pump in a circuit, serving the same role as a water pump in a water circuit. The battery moves the charge from low energy to high energy much like a water pump moves water from low energy to high energy. Both processes require the input of energy to the system. If the battery is the energy input location of a circuit, then the energy output is the motor or the light bulb or the sound amplifier or the ... . In this sense, circuits are all about energy and the battery is the pump that makes it all possible.

Don't be Fooled

Some students falsely believe that a battery supplies the electrons or the protons to an electric circuit. Such students have the false notion that there would be no charge to flow through the circuit if it weren't for the battery. And when the circuit is no longer functional, it is because the battery is out of charge. After all, the battery must be recharged to work again. But don't be fooled! Batteries do not supply charge to a circuit. The charge is already present in the wires of the circuits. Wires consist of atoms and atoms consist of electrons. The use of the phrases rechargeable and recharged are unfortunate misnomers. A battery is actually being re-energized rather than recharged. It's energy-producing ability are being restored by the reversing of the chemical reaction that occurs inside. See Think About It section.

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