Download posttest answers - Aurora City Schools

Answer Key__
Name: __
Pretest score: _____/52
Posttest score: _
52_/52
Ch 16: Electricity
Pretest
N__ unit used to measure resistance
1. __
A. alternating current
B. Ampere
G__ when electrons flow in 1 direction
2. __
C. circuit breaker
D. conductor
Q__ drawing of an electric circuit
3. __
E. Coulomb
F. current
W__ potential difference as a charge moves
4. __
through an electric field
G. direct current
H. electrical charge
L__ a piece of wire in a circuit set to melt and
I. electrical field
break the circuit if it overloads
J. electric force
5. __
F__ flow of electrons through a conductor
6. __
K. electrical potential energy
L. fuse
U__ material that has no resistance at very
7. __
low temperatures
H__ positive (+) and negative (-), like ones repel
8. __
and opposite ones attract
M__ substances that stop electrons from flowing
9. __
M. insulator
N. Ohm
O. parallel circuit
P. resistance/resistors
Q. schematic
R. semiconductors
A__ electrons move back and forth in a
10. __
conductor due to changing electric fields
I
12. __K__ ability to move charges from one area to
11. __ __ a region of space with an electric charge
another
E__ unit of electric charge
S. series circuit
T. short circuit
U. superconductor
V. Volt
W. voltage
13. __
S__ when electricity has only 1 path to follow, no matter how many things
14. __
(e.g. lights) are on it
P__ objects that are connected to an electric current and act to slow the flow
15. __
of electricity
D__ substances that allow currents to flow
16. __
V__ unit of electric potential
17. __
R__ a material that is neither a very good conductor or insulator
18. __
J__ attraction or repulsion between two objects
19. __
T__ an alternate pathway for current from the circuit, often undesirable
20. __
O__ two or more paths for a current to follow
21. __
B__ unit that measures current
22. __
C__ a magnet or strip of 2 metals that opens a circuit when it overloads
23. __
24. - 25. What will these two charges do? Explain why.
They will be attracted and
move towards each other
because they are opposite
charges
26. – 27. The strength of an electric field depends on two things. Name them and
explain whether it is a direct or indirect relationship.
Amount/strength of charge…direct (more
charge = more force)
Distance between charges…indirect (more
distance = less charge)
28. – 30. There are three ways something can become charged. Name/explain them.
Friction…rubbing things together
Induction…one charged thing close to an
uncharged one
Contact…one charged thing touching an
uncharged one
31. – 32. Explain the difference between direct and alternating current and a source
of each.
Direct current is when charges move in one
direction around a circuit. Batteries provide
direct current
Alternating current is when the charges move
back and forth. Your house is alternating
current.
33. Describe the relationship between resistance, voltage and current.
R = V/I
(really I = V/R, flow = push/slowing)
a. resistance stays the same: current increases
if voltage increases. (slowing stays same, flow goes
up if push goes up)
b. current stays the same, increased resistance
needs increased voltage. (flow is the same, so if
slowing goes up, you need more push)
c. voltage remains the same, increased
resistance means decreased current.
(push
remains the same, so if slowing goes up, flow will go
down)
34. – 36. Electric flow is often compared to flow of water. Explain how each picture
shows this for voltage, amperage and resistance.
Voltage =
potential; it’s
the “push”
making
electrons want to move (like water in a
tower vs. on the ground)
Current = flow; it’s how fast the electrons flow
(like flow through a big tube vs little tube)
Resistance = slowing flow; it’s what’s slowing
the electrons down (like squeezing through
a narrow tube)
37. – 42. Identify each of these electric symbols:
wire_
__
battery_
__
__
__
open switch_
__
43. Use the symbols
bulb, 1 battery and
1 switch.
resistor_
light bulb_
closed switch_
__
to draw a simple circuit with 1 light
44. Use the symbols to draw a circuit with 1 battery and two light bulbs connected
in series.
45. For the same circuit as #44, if I add another light bulb what will happen to the
brightness? Explain.
It will decrease (become dimmer)…the voltage
is spread over 3 resistors (push is the same, so
more slowing means less flow)
46. For the same circuit as #44, if I add another battery what will happen to the
brightness? Explain.
It will increase (become brighter)…there is
in creased voltage (more push with the same
slowing means more flow with the same slowing)
47. Use the symbols to draw a circuit with 1 battery and two light bulbs connected
in parallel.
48. For the same circuit as #47, if I add another light bulb what will happen to the
brightness? Explain.
Nothing! Each individual circuit has the same
voltage (brightness) because each individual
circuit has 1 lightbulb. (each “circle” is its own
circuit, so adding a third “circle” still has the same
amount of push, flow and slowing in each circle.)
49. For the same circuit as #47, if I add another battery what will happen to the
brightness? Explain.
Both will increase (become brighter)…there
is increased voltage across each individual
circuit (each “circle” is its own circuit, so adding
more push and keeping slowing the same means more
flow.)
Will the following circuits work (light the bulb)? Explain why.
50.
No…the circuit is not
complete.
51.
Yes…you have a complete
circuit, a power sources
(2 batteries) and a
resistor (light bulb)
52.
A
B
Light A no…the switch
is open
Light B…yes, you have a
complete circuit, a
power source
(battery) and a
resistor (light bulb)