關於市電既電流一問

It depends how your 5Ω resistor is connected to the 25Ω electrical appliance, in series or in parallel. The former arrangement draws a smaller current than if the appliance operates alone. But the latter arragement draws larger current than only when the appliance is in operation.

你的電器本身有25Ω, 跟V=IR歐姆定律, 以純電阻計算會有8.8A電流流經該電器.
若你串聯多一個5Ω電阻, 當然流經該電器的電流會減少. 會有7.33A.

用歐母定律照計，I=V/R , V/25 > V/30。