Transcript 1. What do the direction of forces between opposite charges look like?

1. What do the direction of forces
between opposite charges look like?
+
-
2. When you move two nuclei closer
together, what happens to the force of
repulsion between them?
The closer they get, the stronger
the repulsive force.
3. Why do strands of hair move
towards the comb after you
comb your hair?
The hair gave up electrons to the
comb, so it has a positive charge,
while the comb has a negative charge.
Opposite charges attract.
4. When you bring two charged
balloons closer to each other, what
happens to the forces between them
and what do they do?
The closer the balloons get, the
stronger the forces. Since the
balloons have the same charge,
they repel
5. Label the positive and
negative charges in the picture.
+
-
6. Why are metals good
conductors?
They have loosely held electrons.
7. What causes an electric
current?
Movement of electrons.
8. What is an insulator?
Some thing that resists the
movement of electrons or heat.
9. How can you increase the
current across a resistor?
Increase the voltage or decrease
the resistance.
10. If you have batteries in series,
and one battery goes dead, what
will happen to the current?
The circuit is broken, so there is no
current.
11. If you have batteries in parallel,
and one battery goes dead, what will
happen to the current?
Nothing, each battery has a
separate path.
12. Label the circuits as
series or parallel.
Series
Parallel
Series
Series
13. In a series circuit, what
happens to the brightness if
you add another lamp?
The lamps get dimmer because the
voltage is dived between the
lamps.
14. In a parallel circuit, what
happens to the brightness if
you add another lamp?
Nothing, each lamp has a separate
path to the battery, so each has the
same voltage.
15. In a series circuit, what
happens if a lamp burns out?
The circuit is broken, so all the
lights go out.
16. In a parallel circuit, what
happens if a lamp burns out?
Only that light goes out.
17. What is true about the
voltage in each branch of a
parallel circuit?
They are the same.
18. If you have a 2 ohm and a 4 ohm
resistor in parallel with a 12 volt battery,
what is the current in the circuit?
V=IR so I = V/R,
R= 1/(1/2+1/4)=1.33 ohm
12 v / 1.33 ohm= 9 amps.
19. If you have a 10 ohm, 15 ohm and 30
ohm resistor in series, what voltage will
produce a 1 amp current?
V= IR so add the resistors together.
V = 55 ohms times 1= 55 v
20. What device can increase
or decrease voltage?
A transformer can increase or
decrease the voltage.
21. Where is a magnetic
field the strongest?
At the poles.
22. When two objects of different
temperature are placed together,
what happens to the internal energy
of both?
The warmer object transfers heat
to the cooler object until both are
at the same temperature.
23. What is the freezing
point of water in Kelvin?
oC
Since Kelvin is
plus 273,
o
0 C is 273 Kelvin.
24. What is the boiling
point of water in Kelvin?
oC
Since Kelvin is
plus 273,
o
100 C is 373 Kelvin.
25. If 100 grams of water at 40 oC
is mixed with 100 grams of water
o
at 20 C what will be the final
Temperature of the water?
Since the mass of both water samples
is the same, we can average the
temperatures.
40 oC + 20 oC = 60 oC,
60 / 2 = 30 oC
26. Which solid has the
highest specific heat ?
A, since
the temp
changes
the least
with the
addition
of heat
27. Which way does heat
flow?
From hot to cold.
28. What do the laws of
Thermodynamics tell us about
energy and entropy?
That the Universe tends to move
towards more disorder
(randomness)and less useful
energy.
29. Which phase has the
most entropy?
Gas, since the molecules are spread
randomly.
30. Which phase has the
least entropy?
Solid, since the molecules are
arranged in a pattern.
31. How much heat has to be added
to the substance to change it from a
solid to a liquid?
From 40kJ
to 80kJ, so
40kJ
added.
32. What does a wave carry?
Energy, the matter only moves in
circles.
33. What is the frequency of a wave
with a velocity of 10 m/s and a
wavelength of 2 meters?
V=‫ג‬xf
So f= v/‫ג‬
10 m/s/2 m = 5/sec or 5 Hertz
34. What does amplitude measure
in a wave?
How much energy it carries.
35. A disturbance that only sends
one wave is called a ….
A pulse.
36. If you are 1000 meters from a
noise, how long until you hear it? (use
340 m/s for speed of sound)
V=d/t so t = d/t
1000m/ 340 m/s= 2.94 sec
37. Which part of the EM spectrum
has the shortest wavelength? Gamma
Gamma,
38. Which part of the EM spectrum
has the longest wavelength? Radio
Radio,
39. As a longitudinal wave passes
through a medium, how do the
particles of the medium move?
Parallel to the direction of the
energy.
40. Circle the part of the graph
that shows the loudest sound.
41. Put an x on the part of the
graph that shows the quietest sound.
42. How does the speed of a radio wave compare to the speed
of sound?
Speed of light 300,000,000 m/s compared to speed of sound 340 m/s.
Many times faster.
43. What does the angle of
reflection equal?
The angle of incidence.
44. What happens to the pitch of the
sound from an object moving away
from you?
It gets lower since it takes longer
for each wave to reach you.
45. What happens to the pitch of the
sound from an object moving towards
you?
It gets higher since each wave gets
to you faster than the one before.
46. What is it called when waves
spread out after passing through a
hole in a barrier?
Difraction.
47. Light exhibits the properties of
both…..
Waves and particles.
48. Which color has the shortest
wavelength?
Violet
49. Which color has the longest
wavelength?
Red
50. A convex lens produces a
(virtual/real) image.
Lens that converges (brings
together) light rays.
Forms real images and virtual
images depending on position
of the object. In a real image the
light rays intersect at the image
location.
51. A concave lens produces a
(virtual/real) image.
Virtual, recall that a virtual
image means no light rays
reach the image location.
52. When electrons in an atom
change levels, the atom emits….
A specific spectrum of color based
on the energy level of the electron.
53. The photoelectric/
photoemissive effect means…..
many metals emit electrons
when light shines upon them.
Electrons emitted in this manner
may be called photoelectrons.
54. When the intensity of light increases,
what happens to the number of
photoelectrons that are emitted?
The number increases.
55. How much energy is used by a
500 watt dryer that runs for 2½ hours?
Energy is measured in Kilowatt hours
(KwH).
500 watts times 2.5 hours=
1250 watt hrs. Divided by 1000 to
change to Kwhr = 1.25 Kwhr
56. Inside the atom, what force holds
the protons and neutrons together?
The strong force.
57. Inside the atom, what force
holds the electrons to the atom?
The weak force.
58. Inside the atom, which is
stronger, the strong force or the gravity
between the particles?
At the distances inside the atom,
the strong force is stronger.