JEOPARDY: Kinematics Test - Ehsfaculty.org

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QUIZ 9

REVIEW


Electrostatics [Chapter 22]


Concepts


1.

Which charges get transferred, and why?



2.

Describe the structure of an atom.



3.

State the Basic Law of Electrostatics

in words.




4.

Do the following pairs of objects attract, repel, or neithe
r?



a)

Two protons




b)

A proton and an electron




c)

A neutron and an electron




d)

A polar water molecule and a positively charged rod




e)

Two electrons




f)

Two neutrons




g)

An electron and a nonpolar methane molecule


5.

State the Law of Conse
rvation of Charge in words.




6.

Suppose that a piece of wool flannel is used to rub a plastic rod, both initially
neutral in charge, until the rod has a charge of

18 millicoulombs. According to the
Law of Conservation of Charge, what is the charge on t
he flannel after it has been
used to charge the rod?


7.

How does something become charged by friction?



What is true about the charge on each afterwards?



What are some examples of charging by friction?



8.

How do you use the triboelectric sequence

to figure out what type of charge results
on each insulating material when they are rubbed together to produce a static
electrical charge?



9.

What is charging by contact?



What conditions are required?



Do the objects end up with the same charge o
r opposite charges afterwards?


What is an example of this?



10.

What is charging by induction?



What kind of charge is temporarily produced in this process?


What is an example of this?



11.

How do neutral polar molecules behave differently aroun
d charged objects than
neutral nonpolar molecules?




12.

What is the difference between a conductor and an insulator? List examples of each.







Calculations

The calculations on this quiz involve essentially only simple arithmetic.

Refer to the “Elec
trostatics Practice” worksheet and the Coulombo’s Law notes

for examples.



Important note about the lab:


Make sure you understand the
Electrostatics lab scenarios
. There will be fill
-
in
-
the
-
blank questions to test your understanding of the lab, regardi
ng the attraction of
the water to the charged rod, the process by which the balloon was charged when
rubbed against hair, why the balloon stuck to the glass/wall/chalkboard, and the
use of the triboelectric sequence.












Concept Answers


1.

Electro
ns are the charge carriers (protons stay put): this is because they are less
massive, and found in the outer portion of the atom.

2.

Atoms are mostly empty space. There is a compact nucleus, where the protons and
neutrons reside, surrounded by “clouds” o
f electrons.

3.

Basic Law of Electrostatics:
Opposite charges attract, like charges repel.


4.

a.

repel

b.

attract

c.

neither

d.

attract



e.

repel

f.

neither

g.

neither


5.

Law of Conservation of Charge
:
Charge is neither created nor destroyed, only
tra
nsferred; the total amount of charge in an isolated system remains constant.


6.

The charge on the flannel will be

18 millicoulombs after rubbing the rod.

7.

Charging by friction:
Two solid insulators, initially neutral, are
rubbed together.
Both objec
ts end up with

the opposite type of charge. An example of this occurs when
socks are scuffed across carpet, or when clothing made of different materials
experiences “static cling” after going through tumble drying.

8.

To use the triboelectric sequence,
find the two materials being rubbed together. The
one higher in the list will lose electrons that pass to the one lower in the list. Since the
higher one in the list lost electrons, it becomes positively charged, and since the lower
one in the list gaine
d electrons, it becomes negatively charged.

9.

Charging by contact
: When an object that already has a net charge on it is
made to touch a second object, charge is exchanged instantaneously. Both objects
end up with the same type of charge, i.e. both end
up positive, or both end up
negative, depending on the type of charge involved initially. An example of this is
when one experiences a shock when touching a metal doorknob.

10.

Charging by induction
: A charged object is brought close but is not allowed t
o
touch a second object. Objects end up with the opposite type of charge. The most
common example of this occurs in the conditions leading up to a lightning strike.

11.

Polar vs. nonpolar molecules
: neutral nonpolar molecules are not attracted by
charge
d objects

they act like neutrons. Neutral polar molecules will be
attracted

by
charged objects, whether they are positive or negative, even though they are not
charged themselves, because they have a negative side and a positive side.

12.

In a conductor
,
charge moves easily (because outer electrons are relatively easily
removed from their parent atoms) and so it can redistribute itself over entire surface.
In insulators, charge

tends to stay put. Most metals are excellent electrical conductors.
Material
s like glass, fur, air, plastic, etc. are excellent electrical insulators.