Answer to Question #143301 in Electric Circuits for abdulwahab halliru

Question

A galvanometer of resistance 50 ohm which gives a full scale deflection of 1MA to be adopted to measure current of up to 5A.
a. Calculate the resistance of the resistor required?
b. If the resistor is made of a material of cross sectional area of 4x10^-4cm2 and resistivity 2x10^-6ohm cm. Calculate its length

Answer 1

a) find the resistance of the shunt from the formula below.

$R_{SH}=\frac{I_{G}}{I-I_{G}}R_{G} = \frac{R_{G}}{I/I_{G}-1}$

$R_{SH}= \frac{50\Omega}{5/0.001-1} = 0.01\Omega$

(b) $I(R)=I−I(r)=5A−0.001A=4.999A;I(R)\times R=r\times I(r);R=\frac{r\times I(r)}{I(R)}=\frac{50\times 0.001}{4.999}=0.01Ohm;L=\frac{4\times 10^{-4} \times 0.01}{2\times 10^{-6}} = 2m I(R)×R=r×I(r);R= I(R) r×I(r) ​ = 4.999 50×0.001 ​ =0.01Ohm;L= 2×10 −6 4×10 −4 ×0.01 ​ =2m$