The article analyses teachers' learning on the use of multiple representations (MRs) in the teaching of Ohm's law, examining them in a lesson study, structured in 18 meetings of 2.5 hours each, that addressed this physics curricular topic for the 3rd grade of high school. The qualitative research involved four teachers who teach physics in Brazilian public schools. The empirical material of the study consists of the transcriptions of the audio recordings of the lesson study sessions, interviews with the teachers at the end of the process, and students' written registers produced during the class. From the participating teachers' perspective, the analysis showed that the emphasis on MRs improved the teaching of Ohm's law because it helped them obtain complementary information - to correlate the different representations; acquire a fuller and deeper understanding of the physics concept; connect the abstract to the concrete - carry out constraint interpretations -- interpreting the physical concept by familiarity and inherent properties, and interpreting and transposing representations; construct in-depth understandings -- interpretations and relationships between tables, graphs and generalization of equations; and develop investigative activities encompassing abstraction, extension, and the relationship between physical quantities. Considering the complexities of MRs, teachers examined what information is actually accessible to students and how they can use it, encouraging them to seek an effective way to integrate several representations to assist in the learning process.