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(a) A velocity selector consists of electric and magnetic fields described by the expressions E = Ek and B = Bj, with B = 24.0 mT. Find the value of E (in kV/m) such that a 780 ev electron moving in the negative x-direction is undeflected. KV/m (b) What If? For the value of E found in part (a), what would the kinetic energy of a proton have to be (in MeV) for it to move undeflected in the negative x-direction? MeVA wire 2.80 m in length carries a current of 7.00 A in a region where a uniform magnetic field has a magnitude of 0.230 T. Calculate the magnitude of the magnetic force on the wire assuming the following angles between the magnetic field and the current. (a) 60.0 :1 N (b) 90.0a l:lN (c) 120 :1\" A wire carries a steady current of 2.20 A. A straight section of the wire is 0.750 m long and lies along the y axis within a uniform magnetic field, I? = 1.90 I: T. If the current is in the positive y direction, what is the magnetic force on the section of wire? Direction A rod of mass 0.720 kg and radius 6.00 cm rests on two parallel rails (see figure below) that are d = 12.0 cm apart and L = 45.0 cm long. The rod carries a current ofI = 52.0 A in the direction shown and rolls along the rails without slipping. A uniform magnetic eld of magnitude 0.290 T is directed perpendicular to the rod and the rails. If it starts from rest, what is the speed of the rod as it leaves the rails? (Assume that the rod is of uniform density.) A current of 23.0 mA is maintained in a single circular loop of 1.10 m circumference. A magnetic field of 0.490 T is directed parallel to the plane of the loop. (a) Calculate the magnetic moment of the loop. :lmA-m2 (b) What is the magnitude of the torque exerted by the magnetic field on the loop? Ah eightturn coil encloses an elliptical area having a major axis of 40.0 cm and a minor axis of 30.0 cm (see figure). The coil lies in the plane of the page and has a 6.30A current flowing clockwise around it. If the coil is in a uniform magnetic field of 2.02 X 10'4 T directed toward the left of the page, what is the magnitude of the torque on the coil? Hint: The area of an ellipse is A = nab, where a and b are, respectively, the semimajor and semiminor axes of the ellipse. :N-m 1/ .3. l 40.0 cm |--30.0 (III'VI A rectangular coil consists of / = 180 closely wrapped turns and has dimensions a = 0.400 m and b = 0.300 m. The coil is hinged along the y axis, and its plane makes an angle 0 = 30.0 with the x axis (figure). B (a) What is the magnitude of the torque exerted on the coil by a uniform magnetic field B = 0.810 T directed in the positive x direction when the current is I = 1.20 A in the direction shown? N . m (b) If you are looking downward from the positive y direction, what is the expected direction of rotation of the coil? O clockwise O counterclockwiseA wire is formed into a circle having a diameter of 12.0 cm and placed in a uniform magnetic field of 3.20 mT. The wire carries a current of 5.00 A. (a) Find the maximum torque on the wire. (in) Find the range of potential energies of the wirefield system for different orientations of the circle. mm: M A particle with positive charge q = 4.81 X 10'19 C moves with a velocity 2} = (4? + 43 k) m/s through a region where both a uniform magnetic field and a uniform electric field exist. (a) Calculate the total force on the moving particle, taking E = (5i + Sj + I?) T and E = (5? j 2k] V/m. (Give your answers in N for each component.) Fx = S N Fy = E N (b) What angle does the force vector make with the positive xaxis? (Give your answer in degrees counterclockwise from the +xaxis.) :] counterclockwise from the +X-axis (c) What If? For what vector electric field would the total force on the particle be zero? (Give your answers in V/m for each component.) E. = :1 W... E. = :1 W... E. = :1 W