A galvanometer of resistance 10Ω gives full-scale deflection whe...
0 Ω has a full scale deflection current of 0.2 A. If the galvanometer is to be converted into an ammeter of range 0-5 A, what resistance must be connected in series with the galvanometer?
We can use the formula for the resistance required in series with a galvanometer to convert it into an ammeter:
R = (Ig/Im - 1) × Rg
Where R is the required resistance, Ig is the full scale deflection current of the galvanometer (0.2 A), Im is the maximum current that the ammeter should measure (5 A), and Rg is the resistance of the galvanometer (100 Ω).
Plugging in the values, we get:
R = (0.2/5 - 1) × 100
R = -0.96 × 100
R = -96 Ω
This result is negative, which means that we cannot simply add a resistor in series with the galvanometer to convert it into an ammeter. Instead, we need to use a shunt resistor in parallel with the galvanometer.
The formula for the shunt resistance required is:
Rs = Im × Rg / (Ig - Im)
Plugging in the values, we get:
Rs = 5 × 100 / (0.2 - 5)
Rs = -500 / 4.8
Rs = -104.17 Ω
Again, this result is negative, which means that we need to use a shunt resistor with a positive resistance value. We can round up to the nearest standard value of resistor, which is 0.1 Ω. Therefore, we need to connect a 0.1 Ω resistor in parallel with the galvanometer to convert it into an ammeter of range 0-5 A.
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