The dashed lines in the figure below represent equipotentials (with magnitudes l

Question

The dashed lines in the figure below represent equipotentials (with magnitudes labeled in the margins of the drawing) in a region in which there is an electric field. Also shown are four circles at different distances from point P. Six points on these circles are labeled A to F. A positive point charge at rest is moved in a straight line from P to each of the six labeled points in turn It also ends at rest at these points. Rank the work that must be done by an external agent in order to move the positive charge from P to the labeled points A-F. Greatest 1 _____2 _____3_____4 _____5______6_____least The dashed lines in the figure below show equipotentials in a region in which there is an electric field. A positive point charge is placed at each of the labeled points in turn. In the diagram above, draw arrows to show the direction of the force on the charge at each of the labeled points. Explain.

Explanation / Answer

1) Greater work is done when we move a positive charge from a lower to a higher potential. So we need to rank the points accordingly.

F, A, (P=) E, D, C, B

Above is the decending order of potentials. So yes, you are right.

2)We need to follow two basic points when addressing these kind of questions.

First, the direction of electric field or force is perpendicular to the direction of the equipotential lines.

Second, the electric field is directed from higher to lower potential.

So, you simply need to draw an arrow at each point that is perpendicular to the equipotential and directed toward decreasing potential.

If up is North, as in a map,

at F, the arrow is toward Norh-East (closer to North than East); similar is the case with P.

at A, the arrow is toward Norh-East.

at C, it is North, straight up; similar is at B.

at E, it is mostly North, but slightly West-ward.

at D, it is North, but more West-ward than at E.

(Let me know if more clarification is needed.)

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