Current Electricity and Electrical InstrumentHard
Question
The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100 W and 200 V lamp when not in use?
Options
A.40 Ω
B.20 Ω
C.400 Ω
D.200 Ω
Solution
Rhot 
= 400Ω
cold resistance = Rhot/ 10 = 400/10 = 40Ω
= 400Ω cold resistance = Rhot/ 10 = 400/10 = 40Ω
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