Final answer:
The magnitude of the electric field between the plates of the parallel plate capacitor is 0.25 V/mm.
Step-by-step explanation:
A parallel plate capacitor is made from two small conducting plates that are separated by a distance of 6 mm. The upper plate acquires an excess of positive charges, while the bottom plate acquires a balanced number of negative charges. When the battery is disconnected and a digital voltmeter is used to measure the potential difference between the plates, it reads +1.5 volts. In this scenario, the electric field between the plates is uniform.
The magnitude of the electric field can be determined by dividing the potential difference ΔV by the distance between the plates d. In this case, the magnitude of the electric field is ΔV/d = 1.5 V / 6 mm = 0.25 V/mm.