\begin{align} \text{Per a calcular la variació de la intensitat hem de} :&\cssId{Step1}{I_{20} =\frac{U}{R_{20}}}\\[3px] &\cssId{Step2}{I_{20} =\frac{230}{60,16}}\\[3px] &\cssId{Step3}{I_{20} = 3,823 A }\\[3px] &\cssId{Step4}{I_{600} =\frac{U}{R_{600}}}\\[3px] &\cssId{Step5}{I_{600} =\frac{230}{74,12}}\\[3px] &\cssId{Step6}{I_{600} =3,103 A }\\[3px] &\cssId{Step7}{ {} {} }\\[3px] \text{Per tant}: &\cssId{Step8}{\Delta I = I_{600}-I_{20} }\\[3px] &\cssId{Step9}{\Delta I = 3,103-3,823 }\\[3px] &\cssId{Step10}{\Delta I = -0,720 A }\\[3px] \end{align}