What potential difference is needed to send a current of $6\,A$ through an electrical appliance having a resistance of $40\Omega $ ?

Hint: In order to solve this we need to understand electric current and production of heat using current. Electric current is defined as total charge crossing per unit area. Actually when the electrical circuit is subjected to potential difference then an electrical field is set up in wire which binds the electrons to move in opposite direction as of the applied electrical field which in turn allows electric current to flow in direction of electric field or in direction of decreasing potential. When an electric current flows inside wire then wire opposes this behavior and generates resistance which dissipates the electrical energy to heat energy.

Complete step by step answer:
Let “V” be the potential difference across the resistance.
Let the resistance be $R = 40\Omega $ (given).
Also it is given in the problem that, current is given as, $i = 6A$.
From definition of resistance we get,
$R = \dfrac{V}{i}$
So voltage we get,
$V = iR$
Putting values we get,
$V = (6A) \times (40\Omega )$
$\therefore V = 240\,volts$

So potential difference across resistance is given as, $240\,volts$.

Note: It should be remembered that there are three types of materials categorized on the basis of materials having resistance, first is insulator having maximum value of resistance so almost no current passes through insulator, second is semiconductor for which resistance is somewhat low than insulator so with some conditions current flow inside semiconductor and third is conductor for which resistance is either zero or very close to zero, so a high electrical current flows through resistance. Metals are examples of conductors.