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ConcepTest #1:
Two spheres can be held and moved
around by insulated handles; the
spheres start in contact with no net
charge.
Consider the following choices:
(i) A negative charge is brought near
the spheres.
3. Negative
1. No net charge
2. Positive
4. Not enough information
(i) The spheres are separated.
(iii) The charge is removed.
i
After the three steps, what would
be the net charge on the right-most
sphere if the two spheres were
a) conductors?
b) insulators?
ii
iii
ConcepTest #2:
At the instant pictured, an electron is a
distance r from a proton (the proton is
held fixed).
+
–
a) At the instant picture, what
direction is the force on the
electron?
b) At the instant pictured, what
direction is the electron moving?
r
Consider the following choices
Think about This:
1. Not moving
4. Right
2. Up
5. Left
3. Down
6. Not enough info
At the location of the electron,
what direction is the electric
field (due to the proton)?
At the location of the proton,
what direction is the electric
field (due to the electron)?
ConcepTest #3:
A dipole has charges +q and –q
separated by some distance. The
dipole sits in a uniform electric field
that points to the right.
What is the direction of the net force
acting on the dipole?
1. No net force
4. Right
2. Up
5. Left
3. Down
6. Not enough info
+
–
ConcepTest #4:
A dipole has charges +q and –q
separated by some distance. The
dipole sits in a uniform electric field
that points to the right.
+
–
What is the direction of the net torque
acting on the dipole? (use the “center”
of the dipole as your reference point)
Think about This:
1. No net torque
4. Into page
2. Up
5. Out of page
3. Down
6. Not enough info
What is the magnitude of the
(net) torque exerted on the
dipole about its center?