11.4 Electrical Potential Difference

Transcription

1 11.4 Electrical Potential Difference

2 Work and Charges In moving a charge through an electric field you must apply a force. The force is applied over a distance, therefore work is done. If you do work on an object you give it energy. In this case, electric potential energy.

3 Electric Potential Energy To push a positive test charge closer to a positively charged sphere, we will expend energy to overcome electrical repulsion. Work is done in pushing the charge against the electric field. The energy a charge has due to its location in an electric field is called electrical potential energy. If the charge is released, it will accelerate away from the sphere and electrical potential energy transforms into kinetic energy.

4 Electric Potential Energy If we push a single charge against an electric field, we do a certain amount of work. If we push two charges against the same field, we do twice as much work. Two charges in the same location in an electric field will have twice the electrical potential energy as one; ten charges will have ten times the potential energy. It is convenient when working with electricity to consider the electrical potential energy per charge.

5 The electrical potential energy per charge is the total electrical potential energy divided by the amount of charge. The concept of electrical potential energy per charge has the name, electric potential. The SI unit of measurement for electric potential is the volt, named after the Italian physicist Allesandro Volta. The symbol for volt is V. Electric Potential Potential energy is measured in joules and charge is measured in coulombs

6 Electric Potential Formula: Electric Potential = Electric Potential Energy / Charge V = W / Q Electric Potential (Volts) Electric Potential Energy (Joules) Charge (Coulombs)

7 Electric Potential V = W / Q A potential of 1 volt equals 1 joule of energy per 1 coulomb of charge.

8 Electric Potential What is the difference between electric potential and electrical potential energy? Electric potential is the potential energy per charge. Electrical potential energy is the energy a charge has due to its location in an electric field.

9 Electric Potential Assessment Questions Example #1 A potential difference of 10 Volts exists between two points, A and B, within an electric field. What is the magnitude of charge that requires 0.02 joules of work to move it from A to B?

10 Electric Potential Assessment Questions Example #2 How much electrical energy is required to move 4µC charge through a potential difference of 36 Volts?

11 Electric Potential Assessment Questions Example #3 If 5 joules of work are required to move 1 coulomb of charge between two points in an electric field, the potential difference between the two is:

12 Electric Potential Assessment Questions Example #4 In an electric field, 0.90 joules of work is required to bring 0.45 coulombs of charge from point A to point B. What is the electric potential between A and B?

13 Electric Potential Assessment Questions Example #5 A proton is moved through a potential difference of 10 volts in an electric field. How much work was required to move this proton?

14 Electric Potential Assessment Questions Example #5 - Thinker If there were twice as much charge on one of the objects: a. Would the electrical potential energy (Joules) be the same or would it be twice as great? b. Would the electric potential (Volts) be the same or would it be twice as great? Twice as much charge would cause the object to have twice as much electrical potential energy, because it would have taken twice as much work to bring the object to that location. The electric potential would be the same, because the electric potential is total electrical potential energy divided by total charge

15 Electric Potential Assessment Questions Example #6 The potential energy (Joules) of a compressed spring and the potential energy of a charged object both depend: a. only on the work done on them. b. only on their locations in their respective fields. c. on their locations in their respective fields and on the work done on them. d. on their kinetic energies exceeding their potential energies.

16 Electric Potential Assessment Questions Example #7 Electric potential (volts) is related to electrical potential energy (Joules) as: a. the two terms are different names for the same concept. b. electric potential is the ratio of electrical potential energy per charge. c. both are measured using the units of coulomb. d. both are measured using only the units of joules.