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 $4\,\mu F$ conductor is charged to $400\, volts$ and then its plates are joined through a resistance of $1\,k\Omega $. The heat produced in the resistance is ............... $J$

If $2.2\, Kwatt$ power is transmitted through a $10\, ohm$ line at $22000\, volt$, the power loss in the form of heat will be ............. $watt$

When a potential difference $V$ is applied across a wire of resistance $R$, it dissipates energy at a rate $W$. If the wire is cut into two halves and these halves are connected mutually parallel across the same supply, the same supply, the energy dissipation rate will become:

Two wires $A$ and $B$ of same material and mass have their lengths in the ratio $1 : 2$. On connecting them to the same source, the rate of heat dissipation in $B$ is found to be $5\,W$. The rate of heat dissipation in $A$ is............ $W$

In the circuit shown, the resistance $r$ is a variable resistance. If for $r = fR,$  the heat generation in $r$ is maximum then the value of $f$ is