A milliammeter of range $$120$$ mA and resistance $$9$$ Ω is joined in a circuit as shown. The meter gives full scale deflection for current I when A and B are used as its terminal. i.e., current enters at A and leaves at ‘B’ [C is left isolated] .T he value of I is ……. A.

Question

A milliammeter of range $$120$$ mA and resistance $$9$$ Ω  is joined in a circuit as shown. The meter gives full scale deflection for current I when A and B are used as its terminal. i.e., current enters at A and leaves at ‘B’  [C is left isolated] .T he value of I is ……. A.

Infinity Learn · Accepted Answer

Let say current I enters at A . ⇒$$ig=120$$ mA goes into galvanometer and remaining (i$$ $$-$$ $$120mA) goes through $$0.1$$ Ω ⇒$$R1=0.1$$Ω, $$R2=0.9$$Ω and $$R=9$$Ω  ⇒Consider $$9$$Ω and $$0.9$$Ω in series. ⇒$$VA-VB=i-igR1=igR2+R$$ ⇒Equating the potential drop across upper and lower branch we get ⇒i−$$120$$ × $$10$$−$$3$$ × $$0.1$$ $$=$$ $$9+0.9$$ × $$120$$ × $$10$$−$$3$$ ⇒$$i-0.120$$ $$=$$ $$11.88$$ ⇒$$i=$$ $$12.00$$ ≃$$12.00$$

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A milliammeter of range 120 mA and resistance $9 Ω$ is joined in a circuit as shown. The meter gives full scale deflection for current I when A and B are used as its terminal. i.e., current enters at A and leaves at ‘B’ [C is left isolated] .T he value of I is ……. A.

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Electrical measuring instruments

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A milliammeter of range 120 mA and resistance 9 Ω is joined in a circuit as shown. The meter gives full scale deflection for current I when A and B are used as its terminal. i.e., current enters at A and leaves at ‘B’ [C is left isolated] .T he value of I is ……. A.

Ready to Test Your Skills?

free study material

A milliammeter of range 120 mA and resistance $9 Ω$ is joined in a circuit as shown. The meter gives full scale deflection for current I when A and B are used as its terminal. i.e., current enters at A and leaves at ‘B’ [C is left isolated] .T he value of I is ……. A.