A falvanometer having a coil resistance of 100 ohms gives a full scale deflection when a current of one milli-ampere is passed through it. What is the value of resistance which can convert this galvanometer into ammeter giving a full scale deflection for a current of 10 amperes ? A resistance of the required value is available but it will get burnt if the energy dissipated in it is greater then one watt. Can it be used for the above described conversion of the galvanometer ? When this modified galvanometr is connected across the terminals of battery, it shows a current 4 amp. The current drops to 1 amp., When the resistance os 1.5 ohm is conneted in series with modified galvanomter. Find the emf and internal resistance of battery.

Answer

`S=0.1/(10-10^(-3))~=0.01Omega, yes, E=2V, r=0.5-0.01=0.49 Omega`.