Meter Bridge: Finding Error in Resistance

[LoveBoy]

Homework Statement

Homework Equations

How to find error in resistance ?

The Attempt at a Solution

I found out the resistance without error.
But What is the way to figure out an error of an instrument ?

 

[ehild]

Write the formula you use to calculate the unknown resistance. You read the position x of the slide contact with error of dx= 0.1 cm (or 0.05 cm). R is a function of x: R=f(x) and its error is dR=f ' (x) dx.
Some people consider the reading error as the smallest scale, other consider half of it as the reading error.
If you do not want to differentiate, calculate the resistance with the reading changed by ± the reading error. If it is ±1 mm, calculate the resistances with x=36.1cm and 35.9 cm, and give the deviation from the resistance calculated with x=36 cm.

 

[LoveBoy]

Write the formula you use to calculate the unknown resistance. You read the position x of the slide contact with error of dx= 0.1 cm (or 0.05 cm). R is a function of x: R=f(x) and its error is dR=f ' (x) dx.
Some people consider the reading error as the smallest scale, other consider half of it as the reading error.
If you do not want to differentiate, calculate the resistance with the reading changed by ± the reading error. If it is ±1 mm, calculate the resistances with x=36.1cm and 35.9 cm, and give the deviation from the resistance calculated with x=36 cm.

As per your given hint,
i calculated resistance.
When x=36.1 cm , R=9.03 ohm
When x=35.9 cm, R=8.96 ohm

give the deviation from the resistance calculated with x=36 cm.

What does that mean ?

 

[ehild]

As per your given hint,
i calculated resistance.
When x=36.1 cm , R=9.03 ohm
When x=35.9 cm, R=8.96 ohmWhat does that mean ?

You got 9 ohm with x=36. So the reading error makes the resistance value deviate about 0.3-04 ohm from the real one. To which answers is it closest?
I suggest to apply the other method, taking the derivative of R=f(x) and multiplying it with the reading error.

 

[LoveBoy]

Right ?

 

[ehild]

Right ?

If l is the length read on the meter, it is right. Take the derivative with respect to l at l=36 cm and multiplied it with Δl=0.1.
It is possible that the error of the reading is considered half of that, then the error of the resistance is also halved.

 

[LoveBoy]

I got it now !
Thanks for your help @ehild

 

[ehild]

You are welcome.