20% part (a) use an "e field sensor" and move it along either equipotential. what can you say about the e field along an equipotential?
a. varies in magnitude and direction, parallel to the equipotential.
b. constant magnitude, but varying direction, perpendicular to the equipotential.
c. varies in magnitude and direction, perpendicular to the equipotential.
d. constant direction, but varying magnitude, perpendicular to the equipotential.
e. constant direction, but varying magnitude, parallel to the equipotential.
f. constant magnitude, but varying direction, parallel to the equipotential.

b. Constant magnitude, but varying direction, perpendicular to the equipotential.

Explanation:

As we know that the relation between electric field and electric potential is given as

here if we say that potential is constant because electric field sensor is moving along equi-potential line.

Then we will say

V = constant

so we have

so electric field will remain constant always in magnitude and always remains perpendicular to the surface

so we have

b. Constant magnitude, but varying direction, perpendicular to the equipotential.

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.