Power can be determine by using three possible ways and there are P = I x V, P =

Question

Power can be determine by using three possible ways and there are P = I x V,
P = V2 / R and P = I2 X R. This experiment will use 2 k resistor which having
resistance accuracy limitation of ±0.25%. The measurement was taken by using
voltmeter with the accuracy limitation within ±0.55% of the maximum range, 10 V to
measure the voltage across the resistor and an ammeter having accuracy limitation
within ±0.40% of maximum range, l0mA to measure the current passing through the
resistor. The voltmeter reads 7.5 V and the ammeter reads 7.5 mA. From these three
equations, which one is the most accurate and justifies the answer.

Explanation / Answer

Answer:- When we use the first equation i.e P = V x I then,
uncertainity in power = 7.5 x 0.0075 x (0.552 + 0.42)0.5
= 0.0120322 %

When we use second equation i.e P = V2/R then,
uncertainity in power = (7.5 x 7.5 / 2000) x (2x(0.552) +0.252)0.5
= 0.0125312 %


When we use second equation i.e P = I2 x R then,
uncertainity in power = 0.0075 x 0.0075 x 2000 x (2 x (0.42) + 0.252)0.5
   = 0.0164594 %


Thus using the first equation will give more accurate answer.

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