Hi, I'm trying to work with the Biot-Savart law to look at the magnetic field strength along the center of an asymmetric solenoid I wrapped. I parameterized the coils with x = r cos 2(pi)t, y = r sin 2(pi)t, and z = D t where r is the radius of the coil layer, D is the diameter of the wire, and t represents the number of coils. I'm having difficulty understanding what the "differential current length element" (dl) is in the equation. I understand the vector will be in the direction of the tangential velocity, but I don't understand the "differential" part. Every other component in the equation is pretty straightforward to me. First I tried dividing the unit vector of the velocity by the length of the curve, but I'm fairly certain that's just wrong. Pardon my ignorance. But I carried out the formula to completion with this and got a cool 2-dimensional function that had an accurately shaped graph, but inaccurate values. Please help me understand what the "differential length" means. Would it just be the unit vector of the direction of current flow? Thank you.