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When the charge is at a distance x then the force acting on the charge trying it pull it towards the conducting plane is given by,
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The work done in moving it away to infinity is given by,
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Electromagnetism has had a profound effect on human civilization. Power generated from large electric generators is distributed around the world bringing light into our lives. Maxwell united electricity to magnetism and uncovered the true nature of light. He also arguably motivated Einstein into developing relativity. Hopefully solving Irodov's problems will deepen your appreciation of the beauty and power of Maxwell's equations.