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A particle having mass 1 g and electric charge 10⁻⁸ C travels from a point A having zero electric potential to a point B having 600 V electric potential. What would be the change in its kinetic energy?

Asked in GSEB Board March 2018 · Work done in moving a charge

• (1) -6×10⁻⁶ erg
• (2) -6×10⁻⁶ J
• (3) 6×10⁻⁶ J
• (4) 6×10⁻⁶ erg

Step-by-step solution

Why the other options are wrong

• (1) Right value, wrong unit: the SI calculation gives -6×10⁻⁶ J, which is -60 erg (since 1 J = 10⁷ erg), not -6×10⁻⁶ erg.
• (3) Sign slip: uses Δ K = q(V_B - V_A) = +6×10⁻⁶ J. A positive charge moving up to a higher potential is pushed back by the field, so it loses kinetic energy.
• (4) Two slips: the sign is reversed (the charge slows down, so Δ K is negative) and the joule value is labelled erg.

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