The applied potential difference across a given resistor is altered so that the heat produced per second increases by a factor of $16.$ By what factor does the applied potential difference change?

$A$ piece of wire of resistance $6 \, \Omega$ is connected to a battery of $12 \, V$. Find the amount of current flowing through it. Now,the same wire is redrawn by stretching it to double its length. Find the resistance of the new (redrawn) wire.

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.

If the work done to take $3 \,C$ electric charge from one point to another point is $15 \,J$,what will be the potential difference between these two points (in $,V$)?

An electric iron draws a current of $0.5\, A$ when the voltage is $200\, V$. Calculate the amount of electric charge flowing through it in one hour. (in $C$)

Find out the following in the electric circuit given in the figure:
$(a)$ Effective resistance of two $8\,\Omega$ resistors in the combination.
$(b)$ Current flowing through the $4\,\Omega$ resistor.
$(c)$ Potential difference across the $4\,\Omega$ resistor.
$(d)$ Power dissipated in the $4\,\Omega$ resistor.
$(e)$ Difference in ammeter readings,if any.