Answer :
Final answer:
To convert a galvanometer into a voltmeter with a 30V range, one must add additional resistance. For a galvanometer with a 100-ohm resistance and full-scale deflection current of 30 mA, an additional 900 ohms is needed, making the closest provided answer 1000 ohms. The correct answer is(c)
Explanation:
To calculate the additional resistance needed to convert a galvanometer into a voltmeter with a 30-volt range, you can use Ohm's law, which is V = IR, where V is voltage, I is current, and R is resistance.
Given that the galvanometer has a full-scale deflection for a 30 mA current and an internal resistance of 100 ohms, we want to find the total resistance that would allow 30 V to produce this same current of 30 mA (or 0.030 A).
First, we calculate the total resistance needed for 30 V to produce a 30 mA current:
Rtotal = V / I = 30 V / 0.030 A = 1000 ohms
Since the galvanometer already has a resistance of 100 ohms, we subtract this to find the additional resistance needed:
R = Rtotal - Rgalvanometer = 1000 ohms - 100 ohms = 900 ohms
Therefore, the closest answer from the options given is c) 1000 ohms (understanding there's a slight mismatch due to rounding).
