Although Ohm's law contains various possibilities in teaching and learning scientific inquiry, it is rare for students to experience an authentic inquiry. Thus, we designed an open-ended in-depth inquiry about Ohm's law and made students conduct it. To do this, we developed a laboratory activity for students following a standard method of Ohm's law experiment. After that, we induced them to discover the faults and difficulties in the existing inquiry method. And then, an open-ended in-depth inquiry experiment was conducted to solve the identified problems. Students considered various experimental equipment such as a Wheatstone bridge, a variable resistor, and graphite. They also developed to investigate contact resistance, device resistance, and thermal noise using creative techniques such as the 4-point probe method. We examined students' learning through the activity and their recognition of it. As a result of the open inquiry, students can make various creative efforts to obtain reliable theoretical and experimental results. They showed diverse modeling activities like scientists and thought positively about the inquiry. This study expects science learning to be transformed into "doing science" to help students foster not only a broader understanding of the nature of scientific inquiry (NOSI) but a confirmation of the nature of scientific knowledge (NOSK).