The Current Sensitivity of a Galvanometer Increases by 20%. If Its Resistance Also Increases By 25%, the Voltage Sensitivity Will ____

The current sensitivity of a galvanometer increases by 20%. If its resistance also increases by 25%, the voltage sensitivity will 

(i ) decrease by 1% 
(ii) increased by 5% 
(iii) increased by 10% 
(iv ) decrease by 4%

 

(iv ) decrease by 4%

Explanation:

=`"I'"_{"g"}`=`"I"_{"g"}`+`\frac{20}{100}"Ig"`

=`\frac{20}{100}"Ig"`

=1.2 `"I'_{"g"}`

R'=R + `"25"/"100"`R

=`"125"/"100"`R

=1.25 R

`"V"'_{"g"}`=?

`"V'"_{"g"}`=`\frac{"I"'_{"g"}}{"R"'}`

=`\frac{"1.2 I"'_{"g"}}{"1.25 R"'}`

=`\frac{120}{125}`Vg=`\frac{25}{25}`Vg

Calculation for % changes

=`\frac{"V"'_{"g"}-"V"_{"g"}}{"V"_{"g"}}\times100`

=`\frac{\frac{25}{24}"V"'_{"g"}"-V"_{"g"}}{"V"_{"g"}}\times100`

=`\frac{24-25}{25}\times100`

=`\frac{-1}{25}\times100`=4%

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CBSE Class 12 Physics Sample Paper-2022