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Week 8 Practice Problems For the following problems you are only allowed to start with this equation: ~ F~q = q~v × B (1) ~ = IL ~ ×B ~ Fwire I ~ · d~l = µ0 Ienc Ampere’s Law: B (2) (3) Z d~s × r̂ µ I 0 ~ = (4) Biot-Savart Law: B 4π r2 DO NOT take equations directly out of your notes to get your answers. 1. Given the setup illustrated in Figure 1. a) What is the direction of the force on I3 from I1 ? from I2 ? b) If r1 and r2 are fixed, what must be the relationship between I1 and I2 such that I3 does not feel a net force? 2. A cylindrical wire has a radius R and a total current I that is distributed uniformly. Find the expression for the magnetic field inside and outside of the wire. 3. Using the Biot-Savart Law, calculate the magnetic field of a wire, length L, a radial distance r from the center of the wire. 1