Section 1 Electric Potential Chapter 17 Objectives Distinguish between electrical potential energy, electric potential, and potential difference. Solve problems involving electrical energy and potential difference. Describe the energy conversions that occur in a battery.

Section 1 Electric Potential Chapter 17 Electrical Potential Energy Electrical potential energy is potential energy associated with a charge due to its position in an electric field. Electrical potential energy is a component of mechanical energy. ME = KE + PE grav + PE elastic + PE electric

Section 1 Electric Potential Chapter 17 Electrical Potential Energy, continued Electrical potential energy can be associated with a charge in a uniform field. Electrical Potential Energy in a Uniform Electric Field PE electric = –qEd electrical potential energy = –(charge)  (electric field strength)  (displacement from the reference point in the direction of the field)

Section 1 Electric Potential Chapter 17 Potential Difference Electric Potential equals the work that must be performed against electric forces to move a charge from a reference point to the point in question, divided by the charge. The electric potential associated with a charge is the electric energy divided by the charge:

Section 1 Electric Potential Chapter 17 Potential Difference, continued Potential Difference equals the work that must be performed against electric forces to move a charge between the two points in question, divided by the charge. Potential difference is a change in electric potential.

Section 1 Electric Potential Chapter 17 Potential Difference, continued The potential difference in a uniform field varies with the displacement from a reference point. Potential Difference in a Uniform Electric Field ∆V = –Ed potential difference = –(magnitude of the electric field  displacement)

Section 1 Electric Potential Chapter 17 Sample Problem Potential Energy and Potential Difference A charge moves a distance of 2.0 cm in the direction of a uniform electric field whose magnitude is 215 N/C.As the charge moves, its electrical potential energy decreases by 6.9  J. Find the charge on the moving particle. What is the potential difference between the two locations?

Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference Given: ∆PE electric = –6.9  10 –19 J d = m E = 215 N/C Unknown: q = ? ∆V = ?

Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference Use the equation for the change in electrical potential energy. PE electric = –qEd Rearrange to solve for q, and insert values.

Section 1 Electric Potential Chapter 17 Sample Problem, continued Potential Energy and Potential Difference The potential difference is the magnitude of E times the displacement.

Section 1 Electric Potential Chapter 17 Potential Difference, continued At right, the electric poten- tial at point A depends on the charge at point B and the distance r. An electric potential exists at some point in an electric field regardless of whether there is a charge at that point.

Section 1 Electric Potential Chapter 17 Potential Difference, continued The reference point for potential difference near a point charge is often at infinity. Potential Difference Between a Point at Infinity and a Point Near a Point Charge The superposition principle can be used to calculate the electric potential for a group of charges.