Question

A voltmeter of resistance 300 ohm can be used to measure up to 150 volt. Find the value of the shunt to be added to make it an ammeter to measure the flow of 8 Ampere current

Answer 1

Given,

Internal resistance = 300 ohms

n = I′/I

I’ = 8 A

Ig = V / r

Ig = 150/300

Ig = 0.5 A

n = 8/0.5

n= 16

S=r/(n-1)

= 300/(16–1)

S= 300/15

S= 20Ω

Therefore 20 Ω shunt resistance should be connected in parrallelly across ammeter.

Answer 2

Answer:

The value of the shunt is 20 Ω .

Explanation:

Given, a voltmeter of resistance 300 ohm  can be used to measure up to  150 volt.

Current $I$ = 8 A.

Step 1:

A voltmeter is a galvanometer having a high resistance connected in serieswith it .The current through the galvanometer is

        $I_{g} = \frac{voltmeter}{resistance }$ = $\frac{150}{300}$ = $\frac{1}{2}$ A

Now, An ammeter is a galvanometer having a low resistance connected

in parallel with it .

Step 2:

So ,the shut resistance S is determined from

 $\frac{S}{G} = \frac{I_{g} }{I - I_{g} }$

⇒$\frac{S}{300} = \frac{\frac{1}{2} }{8 - \frac{1}{2} }$  = $\frac{1}{15}$

$S = \frac{300}{15}$ = 20 Ω.

Final answer :

Hence , the value of the shunt  is 20 Ω .