Electrical resistivity of a given metallic wire depends upon

$(i)$ Name and state the law that gives the relationship between the current through a conductor and the potential difference across its two terminals. Also,express this law mathematically.
$(ii)$ Draw the $V-I$ graph for this law. Justify your answer.
$(iii)$ Write the name and use of the circuit components whose symbols are given below:
$(a)$ $A$ resistor with an arrow through it.
$(b)$ $A$ circle with a dot inside,connected to two lines.

Which of the following is true for a parallel combination of two resistors?

If $1 \text{ ampere}$ electric current passes through a conductor,how many electrons will pass per second?

The unit of measurement of charge is coulomb.

Two resistors of $3 \Omega$ and $6 \Omega$ are connected in parallel. The equivalent resistance $R$ is: