The coil of a galvanometer has a resistance of 18.5?, and its meter deflects ful
ID: 2265564 • Letter: T
Question
The coil of a galvanometer has a resistance of 18.5?, and its meter deflects full scale when a current of 8.33 mA passes through it. To make the galvanometer into an ammeter, a 26.7-m ? shunt resistor is added to it. What is the maximum current that this ammeter can read?
Explanation / Answer
The shunt resistor is placed in parallel to the galvonometer. Therefore, the voltage drop across both is the same. So, using V = IR on both galvonometer and shunt and setting them equal:(18 ohms)(galv current) = (26.7 m-ohms)(shunt current)
shunt current = (galv current) (18 / 0.0267)
Total current = galv current (1 + 18 / 0.0267)
Plug in the max current of 8.33 milli amps into that equation to get the maximum total current.