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Question

A voltage V1 is measured 100 times and its average and standard deviation are 100 V and 1.5 V respectively. A second voltage V2, which is independent of V1, is measured 200 times and its average and standard deviation are 150 V and 2 V respectively. V3 is computed as: V3 + V1 + V2. Then the standard deviation of V3 in volts is ________

V1 = 100 ± 1.5 V

V2 = 150 ± 2 V

V3 = V1 + V2

Standard deviation in V3 will be

\({\sigma _{{V_3}}} = \sqrt {{{\left( {\frac{{\partial {V_3}}}{{\partial {V_1}}}} \right)}^2}\sigma _{{V_1}}^2 + {{\left( {\frac{{\partial {V_3}}}{{\partial {V_1}}}} \right)}^2}\sigma _{{V_2}}^2}\)

\(\frac{{\partial {V_3}}}{{\partial {V_1}}} = 1,\frac{{\partial {V_3}}}{{\partial {V_2}}} = 1\)

\({\sigma _{{v_3}}} = \sqrt {{{\left( 1 \right)}^2} \times {{\left( {1.5} \right)}^2} + {{\left( 1 \right)}^2} \times {{\left( 2 \right)}^2}}\)

\({\sigma _{{v_3}}} = 2.5\:V\)

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Important Questions from Error Analysis

  1. The measurement errors mainly caused by human mistakes are called-

  2. A tangent galvanometer is a:

  3. Null type recorders are __________ recorders.

  4. What is the smallest change in the input signal that can be detected by an instrument called?

  5. Errors that occur after taking care of all gross and systematic errors are called as:
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