An ammeter `A` of finite resistance, and a resistor `R` are joined in series to an ideal cell `C`. A potentiometer `P` is joined in parallel to `R`. The ammeter reading is `I_(0)` and the potentiometer reading is `V_(0)`. `P` is now replaced by a voltmeter of finite resistance. The ammeter reading now is `I` and the voltmeter reading is `V`.