How is a voltmeter connected in the circuit to measure the potential difference between two points?

Calculate the number of electrons constituting one coulomb of charge.

Use the data in the table to answer the following: Which among iron and mercury is a better conductor?
< p style="text-align:center"> < span style="font-size:14px"> < u> < strong>Electrical resistivity of some substances at $20\,^oC$

Material	Resistivity $(\Omega \,m)$
Iron	$10.0 \times 10^{-8}$
Mercury	$94.0 \times 10^{-8}$

How can three resistors of resistances $2\, \Omega$,$3\, \Omega$,and $6\, \Omega$ be connected to give a total resistance of $1\, \Omega$?

An electric lamp of $100 \,\Omega$,a toaster of resistance $50 \,\Omega$,and a water filter of resistance $500 \,\Omega$ are connected in parallel to a $220 \,V$ source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances,and what is the current through it?

Show how you would connect three resistors,each of resistance $6 \, \Omega$,so that the combination has a resistance of $(i)$ $9 \, \Omega$,$(ii)$ $4 \, \Omega$.