Magnetic-07-PROBLEMS

PROBLEMS 1. A current of 10 A flows around a closed path in a circuit which is in the horizontal plane as shown in the figure, the circuit consists of D eight alternating arcs of radii r =0.08 m and r =0.12 m. Each sub- 1 2 tends the same angle at the centre. (a) Find the magnetic field produced by this circuit at the centre. (b) An infinitely long straight wire carrying a current of 10 A is passing through the centre of the above circuit vertically with the direction of the current being into the plane of the circuit. What is the force acting on the wire at the centre due to the current in the circuit ? What is the force acting on the arc AC and the straight segment CD due to the current at the centre ? 2. Three infinitely long thin wires, each carrying current i in the same direction are in the x-y plane of a gravity free space. the central wire is along the y-axis while the other two are along x = ±d. (i) Find the locus of the points for which the magnetic field B is zero. (ii) If the central wire is displaced along the z-direction by a small amount and released, show that it will execute simple harmonic motion. If the linear density of the wires is  , find the frequency of oscillations. [ 3. An electron gun G emits electrons of energy 2 KeV travelling in the positive x-direction. The electrons are required to hit spot S where GS = 0.1 m, and the line GS makes an angle of 600 with the x-axis as shown in fig. A uniform magnetic field → parallel to GS exists in the region outside the electron gun. Find the minimum X value of B needed to make the electrons hit S. y 4. A straight segment OC (of length L) of a circuit carrying a current I is placed along the x-axis. Two infinitely long straight wires A snd B, each extending from z = -  to +  , are fixed at y = - a and y = + a respectively, as shown in x the figure. If the wires A and B each carry a current I into the plane of the paper, obtain the expression for the force acting on the segment OC. What will be the force on OC if the current in the wire B is reversed ? z

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