Question

what is the direction of the electric field at b?
a) toward a
b) toward d
c) toward c
d) into the page
e) out of the page

Explanation:

Electric field lines point from regions of higher electric potential to lower electric potential. Point B is on the 0 V equipotential, point A is on +40 V (higher potential), point D is on 0 V (same potential as B), point C is on +20 V (higher potential than B). The electric field direction is toward lower potential, so from higher potential (A, C) to lower (B). Among the options, the only direction that aligns with moving to lower potential is toward D is incorrect (same potential), toward A/C is higher potential, so the correct direction is toward D is wrong, wait no: Wait, electric field points from high to low potential. B is at 0V, A is +40V, so field points from A to B, meaning at B, the field points toward lower potential? No, wait: the electric field direction is the direction a positive charge would move, which is from high potential to low. So at point B, the field points away from higher potential (A, C) toward lower potential. The lower potential from B is toward D (0V is same? No, wait the rightmost is +40, then +20, 0, -20 etc. Wait B is on 0V, D is on 0V (same equipotential), A is +40 (higher), so the field at B points toward lower potential, which is toward the left (toward D? No, D is same potential. Wait no, the equipotentials: right side is +40, +20, 0, -20, -30 etc. So potential increases to the right. So electric field points from right (high) to left (low). So at B (0V), the field points to the left, toward D? No, D is on 0V. Wait no, the options: a) toward A (right, higher potential, wrong), b) toward D (left, lower potential direction, since left of 0V is -20, which is lower), c) toward C (right, higher, wrong), d/e are into/out of page, but equipotentials are in plane, so field is in plane. So the correct direction is toward D, as that is the direction of decreasing potential.

Answer:

b) toward D