In an X-ray tube, electrons are accelerated across a 10 cm gap by a uniform electric field of magnitude 100 kN/C that points from the target back toward the electron source. Taking the source as x_i = 0 and the target as x_f = 0.10 m, and using delta V = -E(x_f - x_i), what is the potential difference between the source and the target?

1. Because the field points from the target back to the source, it points in the negative x direction, so E = -100 x 10^3 N/C. 2. delta V = -E(x_f - x_i) = -(-100 x 10^3 N/C)(0.10 m - 0) = +1.0 x 10^4 V. 3. The potential difference works out positive, meaning the target sits at higher potential than the source. 4. Option A keeps the correct size but drops the sign, missing that two negative signs in this setup cancel out, which is the trap in this problem. _Source: OpenStax Physics (CC BY 4.0), Ch 18 "Static Electricity", section 18.4 Electric Potential_