We know Total Magnetic Flux B = B_0 + B_m Where, B_0 is the external field and B_m is the field inside a material. Now, we get, B = B_0 + μ_0*M (M is the magnetization) My question is - Do I always have to use μ_0 ? If yes then Why? The material isn't free space, is it? & also B = μ_0*(H + M) , where H is the Magnetic Field Intensity/Strength Same problem here. Do I always have to use μ_0 here too? Why not only μ ?? The main problem is we know Magnetic Field inside a material is B_m = μ_0*M Why we are using μ_0 here while the material isn't free space!? This problem is the main reason of those 2 questions I asked before. Please help..