Review

ReviewCharges have _________________________ associated with their position in an ____________________________

Charges that are moving naturally in an ____________________, lose / gain _______________________________

_____________________ characterizes the charge

Ratio of __________________ per charge is called _____________________

Ratio of ___________________ per charge is called __________________________________________________

Positive charge naturally moves through a _____________________________

Negative charge naturally moves through a ____________________________

Unit Play

Potential in EF of a point chargeWhite board practice:

+ 5.0 C

1.0 m

2.0 m

1. Find the magnitude of the field at point A and at point B.2. Potential energy of a +2.0nC charge at each point (refer to the analogy with PEg)3. Find the change of EPE as the charge moves

A B

Potential in EF of a point chargeWhite board practice:

+ 5.0 C

1.0 m

2.0 m

1. Determine potential difference between the two points.2. Make a conclusion about the potential (magnitude) as the distance to the

charge increases / decreases.3. As you get closer to the positive charge, V is ______________________4. As you move away from the positive charge, V is ___________________

A B

Potential in EF of a point chargeWhite board practice:

- 5.0 C

1.0 m

2.0 m

1. Find the magnitude of the field at point A and at point B.2. Find the change of EPE for a +2nC charge as it moves:

A B

Potential in EF of a point chargeWhite board practice:

- 5.0 C

1.0 m

2.0 m

1. Determine potential difference between the two points.2. Make a conclusion about the potential (magnitude) as the distance to the

charge increases / decreases.3. As you get closer to the positive charge, V is ______________________4. As you move away from the positive charge, V is ___________________

A B

Deriving the formula for potential near a point charge

Potential around a positive charge is _________________

Potential around a negative charge is ________________

Potential is a scalar!

2.0 m

Find the potential midway between the two charges:

a) +2.0 nC and – 4.0 nCb) -2.0 nC and +4.0 nCc) -6.0 nC and +6.0nC

Midpoint problems revisited

2.0 m

Is there a net force on the point between the two charges?Is there a net field between the two charges?Is there a net potential between the two charges?

Midpoint problems revisited

2.0 m

If you know the net field between the charges, you can predict

_________________________________________________________________

If you know the net potential between the charges, you can predict

_________________________________________________________________

Zero V vs. ES equilibrium

What can you say about the two charges if you know that Vnet = 0 at midpoint?

In that case, what can you say about the net field?

What will happen to a ‘stray’ charge if it ends up at that point?

Find the point where Enet and Vnet are 0

2.0 m

Charges: +1.0 nC and – 4.0 nC