Final answer:
The potential difference between the plates of a parallel plate capacitor is 225 V. The potential at a point 1.00 cm from one plate and 3.00 cm from the other plate is zero volts.
Step-by-step explanation:
The potential difference between the plates of a parallel plate capacitor can be calculated using the formula V = Ed, where V is the potential difference, E is the electric field strength, and d is the separation between the plates. In this case, the electric field strength is given as 7.50 x 10^4 V/m and the separation is 0.3 cm. Substituting these values into the formula, we have V = (7.50 x 10^4 V/m)(0.3 cm) = 22500 V/cm. To convert this to volts, divide by 100: V = 22500 V/cm ÷ 100 = 225 V.
For part (b), we can use the concept of equipotential surfaces. When the distance from one plate is 1.00 cm and the distance from the other plate is 3.00 cm, the two points lie on a line perpendicular to the plates. Since the potential at one plate is zero volts, the potential at the point 1.00 cm from that plate and 3.00 cm from the other plate will be the same as the potential at the other plate. Therefore, the potential at that point is also zero volts.