If the resistance of a heating coil is $484\, \Omega$ and the supply voltage is $220\, V\ AC$,how much time in $sec$ will the heater take to raise the temperature of $100\, g$ of water by $50^\circ C$?

If the temperature of the cold junction of a thermocouple is lowered,then the neutral temperature

The heater of an electric kettle is made of a wire of length $L$ and diameter $d$. It takes $4$ minutes to raise the temperature of $0.5 \ kg$ of water by $40 \ K$. This heater is replaced by a new heater having two wires of the same material,each of length $L$ and diameter $2d$. The way these wires are connected is given in the options. How much time in minutes will it take to raise the temperature of the same amount of water by $40 \ K$?
$(A)$ $4$ if wires are in parallel
$(B)$ $2$ if wires are in series
$(C)$ $1$ if wires are in series
$(D)$ $0.5$ if wires are in parallel

$A$ room has an $AC$ running for $5$ hours a day at a voltage of $220$ $V$. The wiring of the room consists of $Cu$ wire of $1$ $mm$ radius and a length of $10$ $m$. Power consumption per day is $10$ commercial units. What fraction of it goes into Joule heating in the wires? What would happen if the wiring is made of aluminium of the same dimensions? $(\rho_{Cu} = 1.7 \times 10^{-8} \, \Omega m, \rho_{Al} = 2.7 \times 10^{-8} \, \Omega m)$

The terminal voltage $V$ across a battery of $emf$ $E$ and internal resistance $r$ can be:

$A$ wire of resistance $10 \, \Omega$ is bent to form a circle. $P$ and $Q$ are points on the circumference of the circle dividing it into a quadrant and are connected to a battery of $3 \, V$ and internal resistance $1 \, \Omega$ as shown in the figure. The currents in the two parts of the circle are