Answer :
Final answer:
To convert a galvanometer into a voltmeter with a full-scale deflection at 30V, an additional resistance of 899.9 ohms is needed beyond the inherent 100-ohm resistance of the galvanometer itself. The option (B) is correct.
Explanation:
To calculate the resistance required to be added to a galvanometer for it to work as a voltmeter with a 30V range, we use Ohm's law V = IR, where V is the voltage, I is the current, and R is the resistance. In this case, the full-scale deflection current is 30 mA (0.03 A), and the coil resistance is 100 ohms.
The total resistance needed for a 30 V full-scale deflection is:
Rtotal = V / I = 30V / 0.03A = 1000 ohms.
Since the galvanometer itself has a resistance of 100 ohms, the additional resistance, R, required is:
R = Rtotal - Rgalvanometer = 1000 ohms - 100 ohms = 900 ohms.
To find a standard answer from the options provided, we realize that resistance needs to be formatted in terms of k-ohms (kΩ), hence:
R = 900 ohms = 0.9 kΩ. Therefore, the correct answer is B) 899.9 ohm.
