Galvanometer to ammeter/voltmeter

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To convert a galvanometer with a resistance of 25 ohms and a full-scale deflection current of 500μA into an ammeter reading 20mA, a shunt resistance calculation is required, yielding a value of approximately 0.641 ohms. For the voltmeter conversion to a full-scale reading of 500mV, the series resistance is calculated using the formula, resulting in a value of 975 ohms. The discussion emphasizes the importance of correctly applying Ohm's Law and the formulas for shunt and series resistance. The calculations for both conversions appear to be validated by participants in the thread. Understanding these conversions is essential for effectively using galvanometers in various electrical measurements.
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Homework Statement



The resistance of a galvanometer coil is 25ohms and the current required for full scale deflection is 500μA.
a) explain how to convert the galvanometer to an ammeter reading 20mA full scale, and compute the shunt resistance
b) explain how to convert the galvanometer to a voltmeter reading 500mV full scale, compute the series resistance

Homework Equations



V=IR
IfsRG= (Ia-Ifs)Rsh
Rsh=(RGIfs)/(Ia-Ifs)

The Attempt at a Solution

RG=25ohms

a)
does Ifs=0.02 or 0.0005A

0.0005A * 25ohms = ( 0.02A- 0.0005A) Rsh ??
Rsh=0.641

b)
 
Last edited:
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Your value for (a) looks okay. How will you approach (b)?
 
idk VV=Ifs(Rsh+Rh)
 
(0.5/0.0005) -25 = 975 ?
 
Looks good.
 
cool beans
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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