A point charge 2×10⁻² C is moved from P to S in a uniform electric field of 30 N C⁻¹ directed along the positive x-axis. If the coordinates of P and S are (1,2,0) m and (0,0,0) m respectively, the work done by the electric field will be

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(3) -600 mJ. For a uniform field the work done by the field is W=q⃗E·⃗d, and ⃗E=30̂i has no y or z component. Displacement ⃗d=⃗r_S-⃗r_P=(0-1)̂i+(0-2)̂j+0̂k, so only dₓ=-1 m matters. W=qEₓ dₓ=(2×10⁻²)(30)(-1)=-0.6 J. W=-600 mJ. The negative sign says the field opposes the motion, since a positive charge is being pushed in the -x direction.

A point charge 2×10⁻² C is moved from P to S in a uniform electric field of 30 N C⁻¹ directed along the positive x-axis. If the coordinates of P and S are (1,2,0) m and (0,0,0) m respectively, the work done by the electric field will be

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