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Write the dimensions of voltage sensitivity (S_V) of a voltmeter.

Asked in GSEB Board March 2020 (old course) · Units and dimensions

Answer: (2) M⁻¹L⁻²T³A¹

Step-by-step solution

Given: the voltage sensitivity S_V of a moving-coil instrument.

Idea: it is the deflection produced per unit potential difference, S_V=θ/V, and a deflection in radian is a pure number.

So [S_V]=1/([V]), with [V]=M¹L²T⁻³A⁻¹.

Inverting every exponent: [S_V]=M⁻¹L⁻²T³A¹.

Check through the instrument itself: S_V=θ/(IR)=(NAB)/(kR), and (A⁻¹)/(M¹L²T⁻³A⁻²)=M⁻¹L⁻²T³A¹ -- the same.

So the voltage sensitivity has the dimensions M⁻¹L⁻²T³A¹.

Why the other options are wrong

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