प्रत्येक R त्रिज्या वाली दो समान वृत्ताकार कुंडलियाँ इस प्रकार संकेंद्रित रखी हैं कि उनके तल एक-दूसरे के समकोण पर हैं। उनमें प्रवाहित होने वाली धाराएँ क्रमशः I और 2I हैं। उनके उभयनिष्ठ केंद्र पर परिणामी चुंबकीय प्रेरण क्षेत्र (magnetic field of induction) कितना होगा? (μ0 = निर्वात की पारगम्यता)

Two long parallel conductors separated by a distance 'd' carry currents I1 and I2 in the same direction. They exert an attractive force 'F' on each other per unit length. If the current in one of them is doubled and its direction is reversed, and the distance between them is increased to 3d, what will be the new value of the force between them?

A velocity selector is to be constructed to select ions with a velocity of 6 km s-1. If the electric field used is 400 V m-1, then the magnetic field to be used is: