This is the 12547th most frequent Polish word.
napięciu
"Tension" or "stress."
In this sentence, 'napięcie' refers to an emotional state or atmosphere, specifically tension or suspense, among the characters in a story.
W filmie było czuć rosnące napięcie wśród bohaterów.
In the movie, the rising tension among the characters was palpable.
Here, 'napięciu' is used in a technical context, referring to electrical voltage.
Przy napięciu 220V to urządzenie działa poprawnie.
At a voltage of 220V, this device operates correctly.
This usage of 'napięciu' is scientific, describing the surface tension of liquids in physics.