Meter Conversion: Rs, Rm, Rt, %Ig, %Is

[Blu3eyes]

Homework Statement

A galvanometer has a coil resistance of 460 Ohms and a full scale deflection current of 100 uA. What shunt resistance is needed to convert this galvanometer into an ammeter which has a full scale deflection current of 200 mA. What is the resistance of the ammeter when it is completed? What percentage of the current flows thru the galvanometer? What percentage of the current flows thru the shunt?

Homework Equations

Rs=IgRg/(I - Ig)
Rm=V/Ig - Rg
Rt=V/Ig or Rg + Rm

The Attempt at a Solution

Rs= 100 uA x 460 Ohms/ (200 mA - 100 uA) =230.115 mOhms

Rm=V/Ig - Rg
Rt=V/Ig or Rg + Rm , either case I don't have V

%Ig=??
%Is=??

 

[gneill]

The galvanometer and shunt resistor form a simple current divider. How do currents divide between two parallel resistive branches?

 

[Blu3eyes]

So, is the current = 200.1 mA and the V=92.046 V.

 

[gneill]

So, is the current = 200.1 mA and the V=92.046 V.

No. It's a current divider that is dividing 200 mA through two paths. One is the galvanometer, which should have 100 μA for full scale deflection, and the rest through the shunt resistor.

Given a current I and two parallel resistances R1 and R2, what's the formula for predicting the current through, say, R1?

 

[rwisz]

I would like to clarify a few points before providing a response to this content. First, it is important to define the units used in the problem. Rs and Rm are commonly used to represent resistance in ohms, while Rt is often used to represent total resistance. It is also important to note that %Ig and %Is are not standard units and their meaning is not clear in this context. It would be helpful to have more information or context to understand what they are referring to.

Assuming that the units are indeed in ohms, the solution provided is correct for calculating the shunt resistance (Rs). However, the formula for Rm is not applicable in this case since we do not have the voltage (V) across the galvanometer. To calculate the resistance of the ammeter (Rt), we can use the formula Rt=V/Ig, where V is the voltage across the shunt resistor and Ig is the full scale deflection current of the ammeter.

To find the percentage of current flowing through the galvanometer (%Ig), we can use the formula %Ig=Ig/I * 100%, where I is the total current flowing through the circuit. Similarly, the percentage of current flowing through the shunt resistor (%Is) can be calculated using the formula %Is=Is/I * 100%, where Is is the current flowing through the shunt resistor.

In conclusion, as a scientist, I would suggest providing more information and context to fully understand the problem and provide an accurate response. Additionally, it is important to use standard units and equations in scientific problems to avoid confusion.