4. A small positive point charge +q is placed at a point P in the electric field produced by a larger positive point charge +Q.
(a) Define *electric field strength*. \\[1]
(b) Draw the electric field lines due to the charge +Q only. \\[2]
[VISUALIZATION: Point charge +Q with at least 6 radial electric field lines pointing outwards, evenly spaced.]
(c) The charge +q is moved from point P to point R, which is further away from +Q. State whether the work done by the electric field on charge +q is positive, negative or zero. \\[1]
[VISUALIZATION: Diagram showing a large positive charge +Q and two points P and R, with R further from Q than P. A small positive charge +q is shown at P.]
Question
Define *electric field strength*. \\[1]
Hint
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Think about how you would measure the strength of an electric field at a point using a test charge.
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Electric field strength at a point is the electric force exerted per unit positive charge placed at that point.
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Question
Draw the electric field lines due to the charge +Q only. \\[2]\n[VISUALIZATION: Point charge +Q with at least 6 radial electric field lines pointing outwards, evenly spaced.]
Hint
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Remember the rules for drawing electric field lines: they originate from positive charges, point in the direction a positive test charge would move, and never cross.
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Radial lines pointing outwards from +Q, straight and not crossing (at least 6 lines shown, evenly spaced with arrows).
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Question
The charge +q is moved from point P to point R, which is further away from +Q. State whether the work done by the electric field on charge +q is positive, negative or zero. \\[1]\n[VISUALIZATION: Diagram showing a large positive charge +Q and two points P and R, with R further from Q than P. A small positive charge +q is shown at P.]
Hint
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Hint
Consider the direction of the electric force exerted by +Q on +q. Is the charge +q moving in the same direction as this force, opposite to it, or perpendicular to it?
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