$A$ coil takes $15\,min$ to boil a certain amount of water,and another coil takes $20\,min$ for the same process. What is the time taken to boil the same amount of water when both coils are connected in series?

Given below are two statements:
Statement $I$: $A$ uniform wire of resistance $80\,\Omega$ is cut into four equal parts. These parts are now connected in parallel. The equivalent resistance of the combination will be $5\,\Omega$.
Statement $II$: Two resistances $2\,R$ and $3\,R$ are connected in parallel in an electric circuit. The value of thermal energy developed in $3\,R$ and $2\,R$ will be in the ratio $3:2$.
In the light of the above statements,choose the most appropriate answer from the options given below.

For the circuit shown in the figure:
$(A)$ The current $I$ through the battery is $7.5 \text{ mA}$.
$(B)$ The potential difference across $R_L$ is $18 \text{ V}$.
$(C)$ The ratio of powers dissipated in $R_1$ and $R_2$ is $3$.
$(D)$ If $R_1$ and $R_2$ are interchanged,the magnitude of the power dissipated in $R_L$ will decrease by a factor of $9$.

In the figure shown below,a resistance of $150.4\ \Omega$ is connected in series to an ammeter $A$ of resistance $240\ \Omega$. $A$ shunt resistance of $10\ \Omega$ is connected in parallel with the ammeter. The reading of the ammeter is $...\ mA$.

Consider four circuits shown in the figure below. In which circuit is the power dissipated the greatest? (Neglect the internal resistance of the power supply)

When a current passes through the junction of two different metals,the evolution or absorption of heat at the junction is known as: