Light of My Heart by Elizabeth St. Michel

When love seems impossible, the heart occupies itself however it can. For Rachel Thorne and Anthony Rutland, the thrill of scientific discovery is a suitable substitute. However, love is tenacious and cannot be suppressed for long.
After surviving an attempted rape by a British soldier, Rachel, a self-taught inventor, leaves Colonial Boston for England at the suggestion of her sister-in-law, Abby. There she hopes to shake off the loathsome past and find a love-filled future.
At Abby’s ancestral home, Belvoir Castle, Rachel meets Abby’s brother Anthony, the brilliant but troubled son of a duke. The two bond over their shared fascination with electricity, and sparks fly in more ways than one. However, a dispute with a family employee turns into a dangerous fiasco that threatens to end Anthony and Rachel’s budding romance—and perhaps even their lives.