Current Electricity and Electrical InstrumentHard

Question

A bulb is connected to an ideal battery of emf 10 V so that the resulting current is 10 mA. When the bulb is connected to 220 V mains (ideal), the current is 50 mA. Choose the correct alternative (s)

Options

A.In the first case, the resistance of the bulb is 1kΩ and in second case, it is 4.4 kΩ.
B.It is not possible since ohm’s law is not followed   
C.The increase in resistance is due to heating of the filament of the bulb when it is connected to 220 V mains
D.None of these

Solution

(i) Rbulb = = 1. kΩ
(ii) Rbulb = = 4.4 kΩ
since increase in temperature increases resistance when it is connected to 220 V mains. 

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