Name two ways that the electromagnetic force and gravitational force are different.

Notes on Electric PotentialElectric Field Imagine we have the Earth and a large

asteroid as shown below.

What will happen to the asteroid? Why?

notes

Notes on Electric PotentialElectric Field Imagine we have the Earth and a large

asteroid as shown below.

What will happen to the asteroid? Why?

It will be drawn toward

the Earth and impact it

from Earth’s gravitational field.

notes

Notes on Electric PotentialElectric Field Now imagine we have the charges shown

below.

1C

-1,000 C

What will happen to the + charge? Why?

Notes on Electric PotentialElectric Field Now imagine we have the charges shown

below.

1C

-1,000 C

What will happen to the + charge? Why?

It will get pulled to the

negative charge

because of their electric field.

Notes on Electric PotentialField Lines So how do we draw this? The type of

charge matters, so we need some way of showing direction and strength. We do this with field lines.

Notes on Electric PotentialField Lines So how do we draw this? The type of

charge matters, so we need some way of showing direction and strength. We do this with field lines.

Scientists decided a long time ago that lines should go out from positive and in to negative.

The vectors always point in the direction of the force that would act on a small positive test charge placed in the field

Notes on Electric PotentialField Lines There are 3 things we need to know about

field lines:

1) + charges move in the direction of the arrow, - charges move backwards.

2) The more closely packed the arrows are, the stronger the electric field is.

3) Unlike gravity, electric field lines can be blocked.

Notes on Electric PotentialElectric Shielding

Metal and conductors shield or change our field lines. This is because electrons in metal can move very easily. Since they can move very easily, they try to spread out into the best configuration possible.

Notes on Electric PotentialElectric Shielding

Metal and conductors shield or change our field lines. This is because electrons in metal can move very easily. Since they can move very easily, they try to spread out into the best configuration possible.

Example: a charged, hollow sphere

The charge spreads evenly, no matter where we place the charge inside!

– –

–

–

– – – –

–

–

–

– –

– –

– – – –

+

Notes on Electric PotentialElectric Shielding

Example: a charged, hollow cube

The charge spreads out to get close to the positive, bu away from other negatives. This causes more to cluster on corners.

–

–

– – – – – – – – –

–

–

–

– – – – – – –

+

Notes on Electric PotentialElectric Shielding

Faraday Cage

Example: a charged, hollow cube

The charge spreads out to get close to the positive, bu away from other negatives. This causes more to cluster on corners.

If we put charges inside a box like this, we can tell how intense the charge is, but not where it's located since it evens out. Places like the FBI make use of this a lot.

–

–

– – – – – – – – –

–

–

–

– – – – – – –

+

Notes on Electric PotentialElectric Potential

Just like how we have gravitational potential energy, we can have electric potential energy.

Think of it like gravity.

Positive charge wants to flow “downhill”. Negative charge wants to flow “uphill”.

Notes on Electric PotentialElectric Potential

Assuming same charges, the farther we get from a charge, the less potential we have. We can draw lines of equipotential around charges. These are like elevation on a map. Charges can move on an equipotential line without using energy!

e-field lines

High potential

equipotential

Low potential circles

Notes on Electric PotentialElectric Potential

Electric Potential formula

move charges around

Notes on Electric PotentialElectric Potential

Electric Potential formula

move charges around

Change in voltage

work done=

___________

charge

Work (J)Charge (C)Voltage (V)

Equations

Equations Electric Field Strength

equations

mor V

Vocabulary Electric Field

Field Lines

Conductor

Equipotential

Electric Potential

Volt

The field created by charges that affects all other charges nearby.

A way of showing what the electric field looks like around a charge.

An object that has free-flowing electrons. These can also shield electrical fields.

Places or curves in an electric field that have the same electric potential energy.

The energy a charge can gain or lose by flowing “uphill” or “downhill” along field lines.

How much energy can be loaded on each Coulomb of charge.

vocab

Exit Question #6

Which way do electric field lines and potential lines run?

a) Both go from + to -

b) Both go around a charge

c) Potential goes from + to -, field lines go around a charge

d) Potential goes from - to +, field lines go around a charge

e) Field lines go from + to -, potential go around a charge

f) Field lines go from - to +, potential go around a charge