Efek Variasi Waktu Dan Jumlah Lilitan Pada Sistem Filter Elektromagnetik Terhadap Penurunan Kadar Pb, Zn Dan Co: (Effects of Time Variation and Number of Turns in Electromagnetic Filter Systems on Decreasing Levels of Pb, Zn and Co). Gravitasi 2020, 19 (2), 40-43. https://doi.org/10.22487/gravitasi.v19i2.15357.