The device used to measure electric potential difference is
A. Ohmmeter
B. Galvanometer
C. Ammeter
D. Voltmeter
Answer: Option D
Solution (By JKSSB Mock Tests)
Voltmeter measures potential difference in volts. Connected in parallel, high resistance. Galvanometer detects small current, can be converted to ammeter/voltmeter. Ammeter for current. Ohmmeter for resistance.
Explanation:
The gravitational potential V inside a uniform solid sphere at a distance r from the center is V = -GM * (3R^2 - r^2) / (2R^3). At the exact center of the Earth, r = 0. Substituting r = 0 gives V = -GM(3R^2) / 2R^3 = -3GM / 2R. The potential is strictly non-zero and highly negative.
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