(Solved): 4. In the figure four particles form a square with side \( a=3 \mathrm{~cm} \) and have charges \( ...

4. In the figure four particles form a square with side \( a=3 \mathrm{~cm} \) and have charges \( q 1=+5 \) \( \mathrm{nC}_{\mathcal{n}} \mathrm{q} 2=-10 \mathrm{nC}_{\mathrm{n}} \mathrm{q} 3=+10 \mathrm{nC} \) and \( \mathrm{q} 4=-5 \mathrm{nC} \). \( (1 \mathrm{nC}=10-9 \mathrm{C}) \). In unit vector notation. Determine the electric field produced by the particles at the center of the square.