Question

Which of the following conclusions were derived from Edison and Sir J.J. Thomsons experiment for thermionic emission?
a. Current flow in the galvanometer shows that particles move in the vacuum between the filaments in the glass bulb.
b. Current flows only when the second filament is at a positive potential with respect to the hot carbon filament heated by the battery.
c. The particles leaving the hot carbon filament heated by the battery are negatively charged and are called electrons.
d. Current flows only when the second filament is at a negative potential with respect to the hot carbon filament heated by the battery

• A. a and d
• B. a, c and d
• C. a, b and c
• D. c and d

Answer 1

Answer: (C)

a, b and c

Edison and Sir JJ Thomson used an evacuated glass bulb to study electrons and their emission. From their experiment they observed that, current flows through the Galvanometer only when the key was connected and the hot carbon filament was placed at negative potential and the other placed at positive potential, suggesting that negatively charged particles move towards positive charge even in vacuum.