10.3 Electric Potential

Electric Potential Electric potential refers to the amount of energy that electrons possess in a circuit.

Electric Potential –example: An apple hanging from a low branch. The apple has potential energy because of its position above the ground. If the apple falls down, it will convert its stored energy, or potential energy, into motion. Suppose an apple is at a higher branch. It would have even more potential energy to convert. Each electron has electric potential energy. Potential energy is the energy stored in an object.

Electric Potential A load (ex. light bulb) converts electrical energy into another form of energy (ex. light energy and heat energy). You can compare this to the water flowing past a water wheel. The wheel converts some of the energy of the water into motion. The water has more energy before the wheel than after the wheel. Therefore, there is higher voltage before the load than after the load.

Potential Difference (Voltage) A battery has chemical potential energy in the electrolyte in its electrochemical cells. The chemicals in the electrolyte react with the electrodes. This causes a difference in the amount of electrons between the two terminals.

Potential Difference (Voltage) –One terminal in a battery has mainly negative charges (electrons). –The other terminal has mainly positive charges. The negative charges (electrons), which can move, are attracted to the positive charges at the positive terminal.

Potential Difference (Voltage) If a conductor, such as a copper wire, is connected to both terminals, then the electrons flow from the negative terminal to the positive terminal. The difference in electric potential energy between two points in a circuit is called the potential difference or voltage (V).

Potential Difference (Voltage) This difference causes current to flow in a closed circuit. The higher the potential difference in a circuit, the greater the potential energy of each electron.

Measuring Potential Difference The potential difference between two locations in a circuit is measured with a voltmeter.

Measuring Potential Difference Example: Connecting wires from a negative terminal on a battery across a voltmeter and then back to the positive terminal. The voltmeter would then display the potential difference of the battery. The SI unit for potential difference is the volt (V).

Measuring Potential Difference A voltmeter must be connected in parallel with a load in the circuit in order to compare the potential before and after the load.

Measuring Voltage Activity Fill in the following table as you follow the steps below Connection of Voltmeter Potential Difference (V) Across the battery Across the light bulb  Construct a circuit using a battery, light bulb, switch, and wires  Connect the voltmeter across the battery  Close the switch and note the potential difference in the table  Repeat the previous three steps after changing the position of the voltmeter, as described in the table

Homework Read pg Answer # 1 - 4, 6 on pg. 303