Lesson_2.5

Lesson_2.5 - Lesson 2.5 Electric Potential 1 Electric...

This preview shows pages 1–4. Sign up to view the full content.

Lesson 2.5 Electric Potential 1. Electric Potential Difference Force experienced by an electric charge in an electric field is a conservative force just the same way as force of gravity is a conservative force. q o F=Eq o Fig. 1 + . . r 1 r 2 v 1 v 2 Fig. 1 Shows an electric field generated by a positive charge. Since E varies with the distance from the charge, the electric field has different values at different points. A charge q o placed in the field experiences a force F = E q o . This force does work on the charge when it is moved. Therefore, we can say that every point in an electric field corresponds to a definite potential . When a conservative force produces a displacement dr, the change in potential energy function is given by: dU = -F.dr Since F = E q o on a test charge, the change in potential energy of the test charge when it is displaced through a small distance dr is given by dU = -q o E dr …1 We use V to represent an electric potential. If the potential at a distance r 1 from the charge is V r1 and the potential at a distance r 2 is V r2 , then the potential difference between the two points is V = V r2 – V r1 Potential difference between two points in an electric field is a measure of the change in potential energy per unit charge . In other words, V = V r2 – V r1 = 0 dU E dr q = = - …2

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2. Electric potential at a point. Potential difference between two points distances r 1 and r 2 from a charge q is given by - = - 2 1 1 2 r r r r dr E v v Since 2 r kq E = , we have: 2 2 2 1 2 1 1 r r r r r r kq v v E dr dr r - = - = - - = 2 1 2 1 r r dr r kq = 2 1 1 r r r kq - - 2 1 2 1 1 1 kq kq kq r r r r = - - + = - If we take V r2 = 0 when r 2 = , we have 1 1 1 r r kq v r kq v r - = - = This means that potential at a point distance r from a charge is given by: kq v r = ….3 This is the absolute potential at a point distance r from the charge q and it is a measure of the work done in brining a unit test charge from infinity to that point. Since potential difference is measured as the work done per unit charge, the unit of potential is J.C -1 and is called the volt (V) 1 V = 1 J.C -1
3. Relation between Electric Potential (V) and Electric Field (E) Equation 1 above is: dU = -q o E dr Since potential difference dV is a measure of the potential energy change dU per unit charge, we can write: dr E q dU dV - = = 0 When we consider the x direction only this can be written as dV = - E x dx dx dV E x - = In other words, the electric filed in the x direction is the negative of the rate of change of potential in the x direction. This relation also indicates that electric field can be measured in a unit called volt per meter (V.m -1 ). Similarly electric field in the y and z directions can be written as:

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 14

Lesson_2.5 - Lesson 2.5 Electric Potential 1 Electric...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online