An electromagnetic launcher, or rail gun, consists of two parallel conducting ra

Question

An electromagnetic launcher, or rail gun, consists of two parallel conducting rails across which is laid a conducting bar, which serves as a projectile. To launch this projectile, the rails are immersed in a magnetic field, and a current is sent through the rails and the bar. The magnetic force on the current in the bar then accelerates the bar (in actual rail guns of this kind, the magnetic field is itself produced by the current in the rails; but let us ignore this complication). Supposed that the magnetic field has a strength of 0.20 T and the bar has a length of 0.10 m and a mass of 0.20 kg. Ignore friction. What current must you send through the bar to give it an acceleration of 1.0x10^5 m/s^2?

Explanation / Answer

Given: Mass of the bar = M = 0.2 kg Magnetic field =B = 0.2 T Lenght of the bar =L = 0.1 m Let , Current must be passing through the bar = I   Accleration of the bar = a = 1 x 105 m/s2 Acc. to Newtn's second law , we have force acting on the bar : F = M a = (0.2 )(1x105) = 0.2 x105 N Magnetic foece actig on the bar : F = IL B In order to attain the acceleratin in the bar , The force on the bar shold equal to magnetic force , so that we can calculate the current required to flow in thw wire thus, F = M a = I L B    or

M a    = I L B    I = Ma / L B      = (0.2 x105) / (0.1)(0.2)     = 104 A Mass of the bar = M = 0.2 kg Magnetic field =B = 0.2 T Lenght of the bar =L = 0.1 m Let , Current must be passing through the bar = I   Accleration of the bar = a = 1 x 105 m/s2 Acc. to Newtn's second law , we have force acting on the bar : F = M a = (0.2 )(1x105) = 0.2 x105 N Magnetic foece actig on the bar : F = IL B In order to attain the acceleratin in the bar , The force on the bar shold equal to magnetic force , so that we can calculate the current required to flow in thw wire thus, F = M a = I L B    or

M a    = I L B    I = Ma / L B      = (0.2 x105) / (0.1)(0.2)     = 104 A

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