$A$ cylindrical conductor of length $l$ and uniform area of cross-section $A$ has resistance $R$. Another conductor of length $2l$ and resistance $R$ of the same material has area of cross-section:

Mention one reason why tungsten is used for making the filament of an electric lamp.

What are the essential requirements of a heater filament?

State Ohm's law.

$(a)$ Name the effect of electric current which is utilised in the working of an electrical fuse.
$(b)$ How is a fuse connected in a domestic circuit?

$(i)$ 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.