To calculate the electric field strength at the midpoint between a +7.5 nC and a -2.0 nC point charge separated by 3.0 cm, use the formula E = k * q / r^2, where k is Coulomb's constant (9 x 10^9 N m²/C²). The distance r is half of the total separation, which is 1.5 cm or 0.015 m. Each charge contributes to the electric field at the midpoint, and the signs of the charges must be considered, as they affect the direction of the field. The electric field strength is the vector sum of the fields due to both charges at that point. Understanding the contributions from both charges is essential for accurate calculations.
