Download I) Two small dipoles are placed right next to each other on the z

I) Two small dipoles are placed right next to each other on the zaxis with the same orientation. They are placed so close together
that the center 2 charges effectively overlap. How much stronger is
the field compared to only one dipole?
A) 1/2 B) 1 C) 2 D) 4 E) Not enough info.
Since the 2 charges in the middle cancel each other out, this
effectively gives a dipole where d’=2d. So the strength of the field will
be doubled.
Two charges located on the z-axis form a small electric dipole. The
positive charge is at +0.1z and the negative charge is at -0.1z.
II) In which direction is the electric field due to these charges,
measured at +10z?
A) +z B) –z C) +x D) –x E) There is no field
The positive charge, the negative charge and the observation point P
are all on a line (the z-axis). The positive charge is closest, so has the
stronger effect, thus the field points away from the positive charge.
III) In which direction is the electric field due to these charges,
measured at +10x?
A) +z B) –z C) +x D) –x E) There is no field
The easiest thing here would be to picture the fieldlines coming from
the + charge to the - charge. You can also look at the vectors, and
notice that both charge cause a component pointing down, and the
components along the x axis cancel.
IV) The field is measured at +3x to be 1N/C. What is the field at
+6z?
A) 1N/C B) 1/2N/C C) 1/4N/C D) 1/8N/C E) 1/16N/C
First thing to realize is that the field along the z axis is 2x as strong as
that along the x axis. Being twice as far away gives a factor of one
over 2 to the third = 1/8. So the answer is 2/8 = 1/4.