Physics 1 Honors: Atoms, Charge, and Static Electricity
Balloons X, Y and Z are suspended from strings as shown at the right. Negatively charged balloon X attracts balloon Y and balloon Y attracts balloon Z. Balloon Z ____. Circle all that apply.
may be negatively charged or may be neutral
What are negatively charged objects?
more electrons than protons (anions)
What are positively charged objects?
more protons than electrons (cations)
What does a coulomb represent?
represents the amount of charge that passes through a common 100-W light bulb in about one second.
What is static electricity?
the accumulation of excess electric charge on an object
In electric force, what happens to charged and neutral objects?
they also attract
In electric force, what happens to opposite and similar charges?
they attract and similar charges repel
What does e stand for?
"elementary" or "fundamental charge" is the charge of one proton, while -e is the charge of one electron
What is the strong nuclear force?
(6 x 10^39 times stronger than gravity) force holding protons and neutrons together inside the atom
What is 1 Coulomb equal to?
- a charge of 1 C is the charge of 6.25 X 10^18 electrons - an average lighting bolt has a charge of 15 C
What are the 4 predominant forces in the universe?
- gravity - weak nuclear force - electromagnetism - strong nuclear force
What does e equal?
1.6 X 10^-19 C
If a neutral atom has 22 protons in its nucleus, the number of surrounding electrons is
22
What percent of an atom is empty space?
99.99%
TRUE or FALSE? An object that is electrically neutral contains only neutrons.
FALSE! It contains the SAME # of protons as electrons making it neutral.
TRUE or FALSE? An object that is positively charged contains all protons and no electrons.
FALSE! It only contains MORE protons than electrons
What must happen in order for the neutral oxygen atom to become negatively charged?
It must gain additional e- to become negatively charged resulting in a NET gain of e-
What must happen in order for the neutral oxygen atom to become positively charged?
It must lose a # of e- to become positively charged resulting in a NET charge of +.
TRUE or FALSE? An object that is negatively charged could contain only electrons with no accompanying protons.
TRUE! It could contain only electrons giving it a net - charge.
When a cloud that is negatively charged on its bottom and positively charged on its top moves over the ground below, the ground acquires
a positive charge
What are repulsive forces?
act between like-charged objects, pushing them away from each other. both objects must be charged but no evidence as to what type of charge
What are attractive forces?
act between opposite charged, pulling them towards each other. at least one object is charged, while the other object could be oppositely charged or neutral
What are all material objects composed of?
atoms
When a negatively charged balloon is placed against a non-conducting wall, positive charges in the wall are
attracted to the balloon
Upon entering the room, you observe two balloons suspended from the ceiling. You notice that instead of hanging straight down vertically, the balloons seem to be repelling each other. You can conclusively say ...
both balloons are charged with the same type of charge
What is charge?
charge is quantized and measure in units of Coulombs (C)
What is electromagnetism?
charge particles attract and repel and form electrical fields of magnetism
What is the law of conservation of charge?
electrons are neither created or destroyed but are simply transferred from one material to another
What happens to electrons when energy is added to an atom?
electrons can be persuaded to leave an atom
What are electrically neutral objects?
equal numbers of protons and electrons
What do you do if both objects are conductors when combining charges?
find the net charge on each after they are pulled away and are no longer in contact.
What do you do if objects are placed together when combining charges?
find their equilibrium (i.e., average).
What is a grand unified theory (GUT)?
holy grail of physics is to discover 1 equation that models all 4 forces
What is Newton's Third law for electric forces?
if one object exerts an electric force on another, then the other object will exert an equal and opposite force in return
What is the weak nuclear force?
inner atom decay, fusion that powers the Sun and Carbon-14 dating
What do you do if objects are pulled apart when combining charges?
make up stays the same as their equilibrium state.
What is gravity?
most common, attraction only force between 2 masses
What are electrons?
negatively charged and are present in the region of space outside the nucleus
When you scuff electrons off a rug with your shoes, your shoes are then
negatively charged.
What are electric forces?
non-contact forces. Any charged object can exert this force upon other objects
When we say charge is conserved, we mean that charge can
only be transferred from one place to another.
What are electrons attracted to?
protons of the nucleus, but are easily removed
What is the equation for calculating charge?
q = ne q = charge (C) n = number of excess protons or electrons (must be whole integers, not fractions)
What is the equation for the law of conservation of charge?
q = qp + qe q = total charge qp = charge of protons qe = charge of electrons
What are protons tightly bound with?
within the nucleus and not removable by ordinary measures