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Explain working of moving coil galvanometer and write its uses. |
Answer» Solution :1. When a current flow through the coil, torque on it is `tau=NIABsintheta`.  2. The FIELD is radial by design so angle between `vecAandvecB` ALWAYS be `theta`. So, maximum torque is given by `thereforetau_(max)=NIAB""...(1)` 3. The magnetic torque NIAB tends to rotate the coil. A spring `S_(p)` provides a counter torque which is given by, 4. Restoring torque produce in spring G as, `taupropphi` `thereforetau=kphi""...(2)` 5. A spring `S_(p)` provides a counter torque which balances the magnetic torque it indicate steady angular deflection `phi`. 6. At steady state, `thereforetau=tau_(max)` `thereforekphi=NIAB""...(3)` 7. Here, k is the torsional constant of the spring i.e. restoring torque per unit twist. 8. Unit of torsional constant is `("Joule")/("Radian")("From "k=tau/phi)` 9. The deflection `phi` is indicated on the scale by a POINTER attached to the spring we have, `phi=((NAB)/k)I""...(4)` The quantity in brackets is a constant for a given galvanometer. `thereforephipropI""...(5)` Uses : (i) To detect the presence of current. (ii) It is used to measure minute electric current. (iii) By using galvanometer, ammeter and voltmeter can be constructed. |
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