In the circuit shown in the original figure, a 150.4 Ω resistance is in series with a parallel combination of an ammeter of resistance 240 Ω and a shunt resistance 10 Ω. The supply voltage is 20 V. Find the ammeter reading in mA.

Question

G1 Physics · Accepted Answer

First find the equivalent resistance of the ammeter-shunt parallel combination: R p R_p R p ​ = (240×10)/(240+10) = 2400/250 = 9.6 Ω. Total circuit resistance: R t o t a l R_total R t ​ o t a l = 150.4 + 9.6 = 160 Ω. Total current entering the parallel branch: I = 20/160 = 1/8 A. Let I A I_A I A ​ be the current through the ammeter resistance 240 Ω and I s I_s I s ​ the current through the 10 Ω shunt. Both branches have the same voltage, so I A ( 240 ) I_A(240) I A ​ ( 240 ) = I s ( 10 ) . I_s(…