Question

2. (Short Circuits) An Ammeter is a device that can measure current through a circuit compo- nent. It is devised to be a device that has a VERY LOW internal resistance r. You use the device by connecting the device in series with the branch of the circuit you want to measure the current through. Suppose you accidentally connected the ammeter in parallel with a bat- tery and another resistor (with resistance R»r). Using Kirchoff's rules, show that when s is tiny, the effective current through part of the circuit becomes absurdly large. (In practice, the current would be huge but not infinite... eventually the power drawn through the wires would fry the ammeter and the wires). Please draw a circuit that represents this incorrect setup.]

Answer 1

solution Circuit olagrum. IW 0 for incorrect setup I- R AY ** * EMF= E Equivalent resistance of the circuit = Req = Revo E (R4%) so I = keer - Rr Applying Kirchoff's law in loop with Ammeter Ir. ( I - II) R = 0 = I, (r+R) IR = E(Rtne Isa E and I-I, = E(R+o) - = ER+Er-ERLE - - Rr As reaR So I, . (I-II) That iu a large current flaws through the Ammeter which will fry the ammeter. Also Req a ý so the efective current I through the circuit becomes absurdilep large, but finite.' Rr Rr