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CBSE Class 12-science Answered

Q1. Increasing the current senstivity of a galvanometer may not necessarily increase the voltage. justify your statement
 
 
Asked by poojaparmar065 | 16 Oct, 2014, 03:05: PM
answered-by-expert Expert Answer
Current sensitivity of a galvanometer is defined as the deflection produced in the galvanometer when a unit current flows through it.
begin mathsize 14px style straight I subscript straight s equals straight theta over straight I equals nBA over straight c end style-----(i)
Voltage sensitivity of a galvanometer is defined as the deflection produced in the galvanometer when a unit voltage is applied across two terminals.
begin mathsize 14px style straight V subscript straight s equals straight theta over straight V equals straight theta over IR equals nBA over cR equals straight I subscript straight s over straight R end style----(ii)
Where n=no of turns in the coil of galvanometer
          B=Magnetic field around coil
          A=Area of coil
          c=restoring torque per unit twist
 
From eq. (i) we can say that current senstivity increases by increasing n, B, A and decreases by c
From eq. (ii) we can say that voltage senstivity increases by increasing n, B, A and decreases by c, R.
In case of current senstitvity if we increase the no. of turns n its current sensitvity  begin mathsize 14px style straight theta over straight I end styleincreases. Since resistance of galvnometer R also increases,voltage senstivity begin mathsize 14px style straight theta over straight V end style remains same or unchanged
Therefore increase in current senstivity of galvanometer may nnot necessarily increase the voltage.
 
 
Answered by Priyanka Kumbhar | 17 Oct, 2014, 10:42: AM

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