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A voltemeter reads up to 3 V. It resista...

A voltemeter reads up to 3 V. It resistance is 200 ohm. It is to be used to measure a potential difference, which may be as large as 60 V. What measures you would take to protect the voltmeter?

Text Solution

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V = 3 volt
Resistance of voltmeter ` = R_(v) = 200 Omega`
`I_(G) = (V)/(R) = (3)/(200)`
`I_(G) = 1*5 xx 10^(-2)A`
Let R is the resistance which is connected in series with the voltmeter to increase its range from 3 V to 60V.
`R = (V)/(I_(G)) -R_(1)`,
` = (60)/(1*5 xx 10^(-2)) - 200`
`= (6000)/(1*5) -200`
`R = 4000-200`
`R = 3800 Omega`
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