# Electric Charge - ETHS

Electronics - Devices

Oct 18, 2013 (4 years and 8 months ago)

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Electric Charge

What is a
charge
?

Scientists don’t really know much about why particles have charge or where it comes
from. What they do know is how to use it, and the properties that it gives
particles and matter in
general. Charge primarily serves to create electrostatic forces between particles. For an in depth
video on the basics of charge,
.

What are some properties of

charge?

Charge comes in two forms, positive and
negative. All charges produce electric potential, and
changes in potential result in electric fields, which in
turn create forces. These forces are either attractive or
repulsive. Opposites attract and like

charges repel.
These forces are what cause electrons to move and
create the electricity that we know and love today!
Charge is also conserved. It can be moved around, but
all matter boils down to small particles with constant
charges that cannot change.

What is charged measured in?

Charge is measured in coulombs. A letter q is usually used to denote charge. One
fundamental unit of charge is that of an electron or proton, which is 1.6 x 10
-
19

C, this is denoted
by the letter e.

What are these
subatomic particles

and what are their
charges?

There are many subatomic particles, but the main
ones are the proton, electron, and neutron. A proton has a
charge of +1e, a neutron has a charge of 0 (
it’s electrically
neutral), and an electron has a charge of
-
1e. Electrons are
fundamental particles, meaning that they are not made of
any smaller particles. Neutrons and protons, however are
quarks and o
ne down quark. An up quark has a 2/3e
charge and a down quark has a
-
up to the total charge of the proton and neutron.

What does charge cause?

Charge is responsible for all electric and magnetic phenomena. This is because elec
tric
charge is responsible for the electromagnetic force and thus causes electromagnetic repulsions
and attractions. Here are a few equations that result from charge:

F=(kqQ)/R
2

E=(kq)/R
2

V=(kq)/R

U=(kqQ)/R

F=qE

U=qV

What effect does charge have
on electric field lines?

Charge causes electric fields.
All electric phenomena are based on
positive charges. Therefore field lines
are based on what a positive test
charge would do. This yields field
lines going out from a positive charge
and going towa
rds negative charge. A
key aspect of field lines is that they
never cross. Larger charges produce
stronger fields and thus more field
lines.

What effect does charge have on
magnetism
?

Moving charge causes magnetism to exist. Electricity comes in two forms, static
electricity and current. Static electricity refers to charge stuck in one place. It is the cause for
everything from the shocks you get from a doorknob to lightnin
g. Current on the other hand
refers to charge in motion. Current is responsible for magnetic fields. Just as any stationary
charge has an electric field, any moving charge has a magnetic field. This is shown and
explained in
this video
.