JEE MainPhysicsCurrent Electricity
A galvanometer gives full scale deflection for a current of 2 mA . It is converted into an ammeter of range 0 to 10 mA by connecting a shunt resistance of 5 , . The resistance of the galvanometer coil is:
Options
- A25 ,
- B20 ,
- C4 ,
- D5 ,
Correct answer
B. 20 ,
Step-by-step solution
Let the resistance of the galvanometer be G . Given, full scale deflection current, i_g = 2 mA . Range of ammeter, I = 10 mA . Shunt resistance, S = 5 , . The formula for the shunt resistance required to convert a galvanometer into an ammeter is: S = i_g G I - i_g Substituting the given values: 5 = 2 G 10 - 2 5 = 2G 8 5 = G 4 G = 20 , Answer: 20 ,