# Chapter 17: Electricity

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15 Νοε 2013 (πριν από 4 χρόνια και 6 μήνες)

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Chapter 17: Electricity

Figure Questions

In answering these questions: sometimes you will find the answer in the caption of the picture or
drawing; other times you will find the answer in the text on the same page as the figure.

17.1 Electric Charge and
Force

Figure 1
:

a. Which way does the static electric charge jump
-

from the doorknob to your finger, or the finger to the doorknob?

b. What kind of floor is likely to cause a buildup of static electric charge? (Read the text to find out)

Figure 2:

a. Wh
en will the balloon be
repelled

by the girl’s hair?

b. When will the balloons be
attracted

to each other

Why It Matters: Benjamin Franklin (1706
-
1790)

1.

What was Ben Franklin successful at in life before the age of 40?

2.

What did Franklin discover about light
ning?

3.

What was the experiment that he did, at great risk to his life, that allowed him to collect electric charge from
a lightning bolt inside a thundercloud?

4.

What did Franklin invent that was related to his knowledge of lightning? How did this devise work
? (see the
picture caption below).

Figure 3
: Electric cords for appliances and other electrical devises are made of two parts.

A. What is the center of the cord made from?

B. This type of material is called an electrical _____________.

C. What is outside

of the cord made from?

D. This type of material is called an electrical _____________.

E. Why is the outside of the cord made from this type of material?

Figure 4:

A _____________ charged rod (or a finger like in figure 1) brought near a metal doorknob i
nduces a
_____________ charge on the side of the doorknob closest to the rod and a __________ charge on the side farthest
from the rod. This ability of one object to cause another object to acquire a charge without actually coming into
contact with it is k
nown as an ____________ charge (read the text to find the answer).

Figure 5:

a.

What happens when a negatively charged object actually touches the doorknob?

b.

What type of charge does the doorknob get as a result of this contact with a negatively charged
object?

c.

What would have happened in this scenario if the object had a positive charge?

Figure 6:

a. When you rub a balloon (which is made of plasticized rubber
-

an insulator) with wool, the balloon
acquires through induction a ____________ charge fro
m the wool.

b. What property of water allows it to be deflected (repelled) by the balloon? (read the text above)

Figure 7:

a.

On the object at left, what would happen if a positively charged object were placed inside the electric
field? Why?

b. On the
object at right, what would happen if a positively charged object were placed inside the electric
field? Why?

Figure 8:

a.

Make a drawing of the left side of the figure. What is causing the electrical field lines to bend away from each
other?

b.

At a great dis
tance from this picture, the electric field looks like that of a single charge with a charge of ____.

17.2 Current

Figure 1:

a.

What is electrical potential energy being compared to in this figure?

b.

What happens to the electrical potential energy as the
distance

between

two charges
decreases
?

Figure 2:

a.

Redraw this figure on your paper.

b.

For a
_________

force

that between two
______

charg
es

electrical potential energy ___________
as the
charges move closer to each other. The opposite holds for the
________
___

force between unlike charges.

Figure 3:

a.

A typical car battery has ___________ _____________ (or voltage) of ______ Volts.

b.

Most batteries are __________________ cells that convert __________ energy into __________ energy.

c.

If a common cell has a potenti
al difference of 1.5 V , how many cells are there inside of a 12V car battery
?
(Hint: 1.5 x ??? = 12V)

Figure 4:

a.

What is the name of the element and its chemical symbol for the
filament

in an incandescent light bulb?

b.

The
___________

of the
filament

of a light bulb

determines how
_________

the bulb will be. The filament of
a 40 W light bulb has a
__________
resistance than the filament of a 100 W light bulb.

c.

A light bulb converts ___________ energy into _________ and _________ energy.

Figure 5:

_____
______ (Si)

and
______________ (Ge)
are two common
________________
. Electronic devices, such
as the computer board shown in
Figure 5,

are usually made of
__________
, i
____________, and semiconductors.

Figure 6:

a.

What is one great advantage of a train
using superconducting magnets to float or levitate above the tracks?

b.

Some metals and compounds have zero resistance when their temperature falls below a
___________

temperature
. These types of materials are called
superconductors
. Metals such as
_________
, ______
, and
___________

and some metal compounds containing
_________
,
__________
, and
__________

become
superconductors below their respective critical temperatures. The critical temperature depends on the
material and ranges from less than
___________

ºC (

458 ºF) to as high as
________

ºC (

189 ºF). The search
continues for a material that is superconducting at room temperature.

17.3 Circuits

Figure 1:

As
Figure 1

shows, electric charges have a complete

_______

to follow. Together, the
_______,

_________

_________, and _________

form an
electric ____________.

In this circuit, the outlet is the
__________

of voltage.
Because of the voltage of the outlet,
__________

move through the
________
and bulbs from one side of the outlet
to the other.

The co
nducting path produced when a
________
, such

as a string of light bulbs, is connected across a source of

voltage is called a

_________ __________
.
Without a complete path and a source of voltage, there is no
________

flow and therefore no
___________
. W
hen there is
no

complete path, the circuit is called an
________

circuit.

Figure 2:

A device called a
switch

can be added to a circuit, as
Figure 2

shows. You use a switch to
________

and
________

a circuit, as you have probably done many times. When you flip a light switch, you either
________

or
_________

the circuit to turn a light
_____ or _______
.

Figure 3:

A diagram that depicts the construction of an electric circuit or apparatus is called a

__________ diagram

Figure 3

shows how the battery, wires, and light bulb can be drawn. The symbols that are used in this figure can be
used to describe any other circuit that has a battery and one or more bulbs.
All electrical devices, from toasters to
computers, can be described by schematic diagrams.

Draw the schematic diagram representing the battery, light bulb and wires in this figure.

Figure 4:

Draw the symbols for the following parts of an electrical circuit:

a.

Battery

b. open & closed switche
s

c. resistor

d. wire

Figure 5:

When light bulbs are connected in
_________
, charges must pass through both light bulbs to complete the
circuit.

When appliances or other devices are connected in a series circuit, as
Figure 5

shows, they form a
_______
_
___________
for charges to flow.

Because there is only
______

path for a charge to follow when devices are
connected in series, the
_________

in each device is the same. Even though the current in each device is the same,
the

____________

may be diffe
rent. Therefore, the
__________
across each device in a series circuit can be
different.

If one element along the path in a

_________

circuit is removed, the circuit will not work. For example, if
either of the light bulbs in
Figure 5

were removed, the othe
r one would not glow. The series circuit would be
______
.
Several kinds of breaks may interrupt a series circuit. An
_________

switch, a
________
-

____

light bulb, a
_____
wire,
or any other interruption can cause the
________

circuit to fail.

Figure 6.

When light bulbs are connected in
__________
, charges have more than one path to follow. The circuit
can be
_________

even if one light bulb burns out.

When devices are connected in
___________

rather than in
series, the
_________

across each device is the

same. The
__________
in each device does not have to be the same.
________

of the currents in all of the devices equals the
_________
current.
If one bulb has less
____________
, more charge moves through that bulb because the bulb offers less
__
__________

to the movement
of charges.

Why It Matters: Science and Society

1.

What was the name of the first computer?

2.

When was it developed?

3.

How big was it?

4.

What devise allowed computers to be smaller and use much less power?

5.

What is the name for these
small modern computers that we all own?

Figure 7.

An electric meter records the amount of__________ consumed.
Electric companies measure energy in
__________
-

_______.
Power companies charge for energy, not _______. The unit of energy that power compani
es
use to track consumption of energy is the kilowatt
-
hour (___•___).In SI units, 1 kW•h = _____ × 10
__

J. Depending on
where you live, the cost of energy ranges from 5 to 20 ______ per kilowatt
-
hour. Power companies use electric
meters

to determine how mu
ch electrical
___________

is consumed over a certain time interval.

Figure 8.

These
_________
are typical for modern electronic devices. The one on the left has been
____________

and
is “blown.” If many devices are connected across an electrical outlet, th
e overall
_____________

of the circuit is
lowered. As a result, the electrical wires carry more than a safe level of
___________
, and the circuit is said to be

which
can cause
_______
.

If a wire’s insulation wears down, two wires may touch and create an
alternative pathway for current, or a
_________
circuit
, which is also a fire hazard.

The lower
___________

greatly
increases the
__________

in the circuit. F
uses
and circuit
___________

can reduce the danger and the threat to
sensitive electronic devices.

(see the text on this page to fill in the blanks)

Figure 9.

Many homes are equipped with
___________ ___________
. They use

a
________

or
____________

strip
, a strip wi
th two different metals welded together, that responds to current overload by
__________

the circuit. The circuit breaker acts as a
___________
. Unlike fuses, circuit breakers can be
_________
by
turning the switch back on.

A
__________ ________ _________
__ _____________

(GFCI) is a special kind of electrical outlet that acts as a
small circuit breaker. These special outlets are often found in
____________ and __________
, where
_________

is
used near electricity.