APPC Electrostatics

Electric Fields and Forces

AP Physics C

Open Ended

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Electric Charge

“Charge” is a property of subatomic particles.
Facts about charge:

■ There are basically 2 types: positive (protons)

and negative (electrons)

■ LIKE charges REPEL and OPPOSITE

charges ATTRACT

■ Charges are symbolic of fluids in that they

can be in 2 states, STATIC or DYNAMIC.

Items on the top more likely to give electrons to those below

​

​Triboelectric Series

Multiple Choice

An atom loses an electron.  What type of charge does it have now?

• positive
• negative

Multiple Choice

An atom gains an electron.  What type of charge does it have now?

• positive
• negative
• No charge

Multiple Choice

Two like charges

•  neutralize each other.
• repel each other. 
• must be neutrons. 
• attract each other.

Electric Charge – The specifics

Some important

constants:

•The symbol for CHARGE is “q”
•The unit is the COULOMB(C),
named after Charles Coulomb
•If we are talking about a SINGLE
charged particle such as 1 electron
or 1 proton we are referring to an
ELEMENTARY charge and often
use, e , to symbolize this.

Particle

Charge

Mass

Proton

1.6x10-19 C

1.67 x10-27 kg

Electron

1.6x10-19 C

9.11 x10-31 kg

Neutron

0

1.67 x10-27 kg

Multiple Choice

The smallest possible unit matter can be divided into while still maintaining its properties.

• Proton
• Atom
• Element

Multiple Choice

Most of the mass in an atom is made up of _____________________?

• protons and electrons
• protons and neutrons
• neutrons and electrons
• electrons and quarks

Multiple Choice

Protons and Electrons balance the total net charge of an atom.

• True
• False

Multiple Choice

What is the fundamental value of  electron charge?

•  e=1.60×10−19 C

• e= 1.60×10−91 C

• e= 1.60×10−15 C

• e= 1.60×10−21 C

Multiple Choice

Which particle does not contribute mass to the atom?

• Proton
• Neutron
• Electron
• Nucleus

Multiple Choice

Which particle is the smallest?

• Proton
• Neutron
• Electron
• Nucleus

Charge is “CONSERVED”

Charge cannot be

created or destroyed
only transferred from
one object to another.
Even though these 2
charges attract initially,
they repel after
touching. Notice the
NET charge stays the
same.

Multiple Choice

The law of conservation of charge states that...

• all atoms have more protons than electrons

• only protons can be rubbed off of an atom

• charge cannot be transferred 

• charge cannot be created or destroyed

Conductors and Insulators

The movement of charge is limited by the substance

the charge is trying to pass through. There are
generally 2 types of substances.

Conductors: Allow charge to move readily though it.
Insulators: Restrict the movement of the charge

Conductor = Copper Wire
Insulator = Plastic sheath

Categorize

Options (16)

lightning rod

copper wire

aluminum

gold

silver

iron

graphite

brass

rubber

glass

plastic

ceramic

wood

air

paper

silicone

Categorize conductor vs insulator

Conductor

Insulator

Charging and Discharging

There are basically 2 ways

you can charge
something.

1.Charge by friction

2.Induction

Induction and Grounding
The second way to charge something is via

INDUCTION, which requires NO PHYSICAL
CONTACT.

Induction/Noncontact: Electrophorus

Multiple Choice

A boy's hair stands up when he goes down a plastic slide. What kind of charging is this?

• Friction

• Induction

Electric Field Springboard

​

Multiple Choice

Does the Earth have an influence on things around it?

• Yes

• No

Fill in the Blank

What is the name of this influence?

Fill in the Blank

What does the Earth have that allows it to have this influence?

Fill in the Blank

What must other objects have to allow them to be influenced by the Earth?

Fill in the Blank

How far does the Earth's influence extend?

Multiple Choice

Suppose an elephant and a mouse find themselves suspended near the surface of the Earth.

a. Which has a greater gravitational force acting on it?

• elephant

• mouse

• same for both

Multiple Choice

Suppose an elephant and a mouse find themselves suspended near the surface of the Earth.

b. Which would undergo a greater acceleration if dropped?

Ignore air resistance

• elephant

• mouse

• same for both

Fill in the Blank

What is the ratio that defines the value of this acceleration?

Gravity

We have called this ratio gravitational acceleration.

AND we have called it gravitational field.

On earth it's 9.8 (roughly 10) and can be measured in m/s² or N/kg.

Either way it is symbolized by g.

Multiple Choice

Does a charged Van de Graaff generator dome have an influence on things around it?

• yes

• no

Fill in the Blank

What does the dome have that allows it to have this influence?

Fill in the Blank

What must other objects have to allow them to be influenced by the dome?

Fill in the Blank

How far does the dome's influence extend?

Multiple Choice

Suppose a small charge and a large charge find themselves suspended near the dome.

a. Which has a greater electric force acting on it?

• small charge

• large charge

• same for both

Electric Field

While the force is greater on the larger charge, the force/charge is the same.

This is called Electric Field


Follows direction of positive "test" charge

Electric Field Lines Examples

​Positive Point Charge

​Negative Point Charge

Attractive Forces

Repulsion Forces

Draw

Draw the electric field lines around the charges

Draw

Draw the electric field around the two charges

Draw

Draw the electric field in an oppositely charged plates

Fields: Invisible/Non-contact Forces

Electrostatic

Gravity

Fg vs Fe

Labelling

Match characteristics of Fg vs Fe

Drag labels to their correct position on the image

Both attractive & repulsive

Fg=Gm1m2/r^2

Fe=kq1q2/r^2

Charge (q)

Mass (m)

Attractive ONLY