Charging and Maintaining Multiple Batteries

If a vacuum tube with a filament rating of 0.25 A and 5 V is operated from a 6 volt battery, what value of resistor is necessary? A.4 ohms. B.5 ohms. C.10 ohms. D.2 ohms. 6A64. A. The minimum power dissipation rating of a resistor of 20,000 ohms across a potential of 500 V should be: A.25 watts. B.12.5 watts. C.15 watts. D.None of the above ... ................
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