Transcript Electro-Statics Think then MC

The sphere on the right has a charge of +2q. The
sphere to the left has a charge of – 3q.
Which
of the
followingdescription
pictorial descriptions
Construct
a pictorial
of the
of
the electric
field that
bestbest
matches
the above
electric
field lines
matches
the
verbal
abovedescription?
verbal description.
2
1
3
4
Jenny, a student in an introductory physics class sees the
following equation:
(1.6 x 10-5 C) (5.0 x 106 N/C) – 10 N = (.015 kg) a
Which
the following
verbal
descriptions
best
Write aofverbal
description
that
best matches
the
matches
the above mathematical
representation?
above mathematical
representation.
1 A proton is in electric field that experiences a 10 N force
holding it back.
2 A mass of 0.015 kg is experiencing just one force due to an
electric field of 5.0 x 106 N/C.
3 A charged particle is being accelerated through an electric
field but also experiences some force in the opposite
direction.
4 A particle has a charge of 1.6 x 10-5 C is being accelerated
only by the result of a 10 N force applied to it.
Two equal magnitude charged spheres are held near each
other. The electric field measured at point A points at a 45o
angle North of West.
Which
of the
following
pictures
Construct
a picture
which
couldbelow
match the
matches
the above description?
above description.
1
3 A
A
2 A
x
x
+q
x
+√2 q
x
+q
x
+q
+q
+q
x
A proton starts at rest between metal sheets with a
potential difference of 100 Volts across them.
Vinit = 100 V
Vfinal = 0 V
Which
of the
following
motionthat
diagrams
could
Construct
a motion
diagram
matches
the
match
themotion
motionwhen
of thereleased.
proton?
proton’s
1
2
3
4
Sara is looking over her physics textbook and sees a
situation described mathematically below.
(3 x 1012 ) (1.6 x 1019 )
I
(3060)
Ne
I
t
The
same the
situation
described
in words
Describe
same is
situation
in words
below.
below. Decide which description fits the
mathematical description best.
1 3 x 1012 protons travel through a wire each hour.
2 3 x 1012 electrons travel through a wire in each hour.
3 3 x 1012 electrons travel through a wire in just under an
hour.
4 3 x 1012 Coulombs of charge travel through a wire in just
under an hour.
A picture is drawn below showing equipotential surfaces for
two fixed charged pith balls.
Which
the following
verbal
descriptions
Write aofverbal
description
that
matches thebest
above
match
the above
equipotential surfaces?
equipotential
surfaces.
1. Both pith balls are positively charged.
2. Both pith balls are negatively charged.
3. One pith ball is positively charged, the other is
negatively charged.
4. Both 1 and 2 are possible solutions
A situation is described with an energy bar chart below.
Ko PEgo PEso PEqo W K PEg PEs PEq Eint
0
Which
the following
verbal representations
best
Write aofverbal
representation
to best match the
matches
thechart.
above bar chart?
above bar
1 A charged object shoots straight up away from another charged object
and reaches its highest point.
2 A charged object is high above the ground in an electric field. The field
pulls the charged particle downward. We see the system’s energy
when it is halfway down to the ground..
3 A charged object initially at rest moves at an angle away from a second
like charged object. At the top of the projectile path the object is moving
horizontally.
4 A proton is held below a negatively charged sphere and released.
Three identical magnitude charged spheres are shown below.
+q1
-q3
+q2
Which
electrical
force diagram
corresponds
to the pictorial
Construct
an electrical
force diagram
to correspond
to the
representation?
pictorial representation for q3.
1
2

Fq2 on q3 y

x
Fq1 on q3

Fq2 on q3 y

x
Fq1 on q3
3
4

Fq2 on q3 y

x
Fq1 on q3

Fq2 on q3

Fq1 on q3
y
x
A student sees in a textbook the picture below of two charged
spheres and the corresponding electric field lines.
Which
of the
following
verbal descriptions
best
Construct
a verbal
description
that best matches
the
matches
the above
pictorial representation?
above pictorial
representation.
1 The two spheres have charges that are opposite but equal
in magnitude.
2 The left sphere has a positive charge that is twice the
magnitude of the negative charge on the right.
3 The left sphere has a negative charge that is twice the
magnitude of the positive charge on the right.
4 The right sphere must not have all of the lines drawn into it.
A positively charged sphere is held in a fixed
position relative to a negatively charged sphere on
the left with half the magnitude of electric charge.
Which
pair of
electric
force diagrams
below that
bestbest
Construct
a pair
of electric
force diagrams
matches
matchesthe
theabove
aboveverbal
verbaldescription?
description.
y
1
y

Fneg on pos
2

Fneg on pos

Fpos on neg
x
y
y
3
y

Fneg on pos
y

Fpos on neg
x
y

Fpos on neg
x
4

Fneg on pos
y

Fpos on neg
x
Four charged spheres, not necessarily the same
magnitude charge, are placed at the corners of a
square. The net electrical force on sphere C is zero.
A
C
B
D
What
Whatare
arethe
thesigns
signsof
ofthe
thecharged
chargedspheres
spheresto
tomatch
match
the
theabove
aboveverbal
verbaldescription?
description?
A
B
C
D
1
+
–
–
+
2
–
–
–
+
3
–
–
+
+
4
+
+
+
+
5
+
–
+
–
A process is shown in the picture below. The charged sphere
on the right is fixed. The left charged sphere is on a
moveable cart. It is initially held by a wedge, then let go.
Initial
+
+

v
Final
+
+
What
energy
chartbar
best
matches
the pictorial
Construct
anbar
energy
chart
that best
matches representation?
the pictorial
Ko PEgo PEso PEqo W K PEg PEs PEq Eint
representation.
1
2
3
A real situation is described mathematically:
½ m vo2 + q Vo = ½ m v2 + q V
½ (.001 kg) (0 m/s)2 + (1.0 x 10-6 C) (12 V) =
½ (.001 kg) v2 + (1.0 x 10-6 C) (0 V)
The
same situation
described that
verbally
below.
Which
Construct
a verbal is
description
fits the
above
description
fitsdescription
the above mathematical
description best?
mathematical
best.
1 A .001 kg object is moving across the plates of a capacitor at a
constant speed.
2 An object whose charge is 1.0 x 10-6 C is initially moving at some
speed, v away from a 12 Volt plate until it comes to rest.
3 A .001 kilogram object that has a charge is initially at rest in a
capacitor but then moves across the 12 Volt potential difference.
4 The plate where the object comes to has no charge on it.