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In the adjoining circuit, the battery $E_1$ has an emf of $12\, volt$ and zero internal resistance while the battery $E_2$ has an $emf$ of $2\, volt$. If the galvanometer $G$ reads zero, then the value of the resistance $X$ (in $ohm$ ) is
An electric kettle has two heating coils. When one of the coils is connected to an a.c. sotuce, the water in the kettle boils in $10$ minutes. When the other coil is used the w’ater boils in $40$ minutes. If both the coils are connected in parallel, the time taken by the same quantity of water to boil will be ...... $min$
One $kg$ of water, at $20\,^oC$, is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of $20\, \Omega $. The rms voltage in the mains is $200\, V$. Ignoring heat loss from the kettle, time taken for water to evaporate fully, is close to.......... $\min$ [Specific heat of water $= 4200\, J/kg\, ^oC$), Latent heat of water $= 2260\, k\,J/kg$]
A storage battery has $e.m.f.$ $15\, volts$ and internal resistance $0.05\, ohm$. Its terminal voltage when it is delivering $10\, ampere$ is ............... $volts$
A wire of resistance $R$ and radius $r$ is stretched till its radius became $r / 2$. If new resistance of the stretched wire is $x R$, then value of $x$ is $\qquad$