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Per NCERT eqn 5.2, the pressure-volume WORK done on a gas at constant external pressure p_ex is given by which expression?
Aw = +p_ex × ΔV
Bw = nRT × p_ex
Cw = −p_ex × ΔV = −p_ex (V_f − V_i)
Dw = p_ex × V_f
Answer & Solution
Correct answer: C. w = −p_ex × ΔV = −p_ex (V_f − V_i)
Per NCERT eqn 5.2, w = −p_ex ΔV. Negative sign so that COMPRESSION (V_f<V_i, ΔV<0) gives w>0 (work done ON system).
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