What will happen to the resistance of the circuit,if the current through it is doubled?

$A$ large number of free electrons are present in metals,yet no current flows in the absence of electric potential across it. Explain the statement with reason.

Give reasons for the following:
$(i)$ Tungsten is used almost exclusively for the filament of electric lamps.
$(ii)$ Why do we use copper and aluminium wires for the transmission of electric current?

What is the cause of resistance?

What is the equivalent resistance of resistors $R_{1}$ and $R_{2}$ connected in parallel connection?

What is meant by resistance of a conductor? Name and define its $SI$ unit. List the factors on which the resistance of a conductor depends. How is the resistance of a wire affected if
$(i)$ its length is doubled,
$(ii)$ its radius is doubled?