Brightness of the bulb decreases gradually with its period of use because of
A. evaporation of metal from filament of bulb
B. decreases in resistance of bulb
C. decrease in electric supply to the bulb
D. None of the above
Answer: Option A
A. evaporation of metal from filament of bulb
B. decreases in resistance of bulb
C. decrease in electric supply to the bulb
D. None of the above
Answer: Option A
What will be the total resistance of the three 20-Ω coils connected in series?
A. 40 Ω
B. 20 Ω
C. 60 Ω
D. 800 Ω
Superconductors are substances which
A. conduct electricity at lower temperature
B. offer high resistance to the flow of current
C. offer not resistance to the flow of current
D. conduct electricity at high temperature
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