Electrical resistivity of a given metallic wire depends upon

$(a)$ Three resistors $R_{1}, R_{2}$ and $R_{3}$ are connected in parallel and the combination is connected to a battery,ammeter,voltmeter,and key. Draw a suitable circuit diagram. Obtain an expression for the effective resistance of the combination of resistors in parallel.
$(b)$ Why are electric bulbs filled with chemically inactive nitrogen or argon?
$(c)$ What is meant by the statement that the rating of a fuse in a circuit is $5 \ A$?

Three bulbs of $40\, W$,$60\, W$,and $100\, W$ are connected in series across the mains. Across which bulb is the potential difference highest? Across which is it lowest?

What is the magnitude of the electric charge on an electron?

If five equal pieces of wire having $5\, \Omega$ resistance are made and connected in parallel,then their equivalent resistance will be $......$

Three resistors of $5 \, \Omega$,$10 \, \Omega$,and $15 \, \Omega$ are connected in series,and the combination is connected to a battery of $30 \, V$. An ammeter and a voltmeter are connected in the circuit. Draw a circuit diagram to connect all the devices in the correct order. What is the current flowing through the circuit and the potential difference across the $10 \, \Omega$ resistor?