Plz help me and how do I calculate “joules” to get my answer...?

  20 Newtons

Explanation:

In this context, 1 J = (1 N)(1 m).

  work = force × distance

  40 N·m = force × (2 m)

  (40 N·m)/(2 m) = 20 N = force

The applied force is 20 Newtons.

Newtons and Joules are "derived" SI units.

  N = kg·m/s²

  J = kg·m²/s² = N·m

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.