Which device works on the heating effect of electric current?

In the given circuit,calculate $(i)$ total resistance of the circuit,and (ii) current shown by the ammeter.

Which of the following substances does not contain free electrons?

In an electrical circuit,two resistors of $2\,\Omega$ and $4\,\Omega$ respectively are connected in series to a $6\,V$ battery. The heat dissipated by the $4\,\Omega$ resistor in $5\,s$ will be ........ $J$.

Three $V-I$ graphs are drawn individually for two resistors and their series combination. Out of $A, B, C$,which one represents the graph for the series combination of the other two? Give a reason for your answer.

$(a)$ How is the direction of electric current related to the direction of flow of electrons in a wire?
$(b)$ Calculate the current in a circuit,if $500 \, C$ of charge passes through it in $10$ minutes.