# Recent questions and answers in Moving charges and magnetism

### Do magnetic forces obey Newton's third law : Verify for two current elements $\overrightarrow{dl_1}= dl \hat i$ located at the origin and $\overrightarrow{dl_2}= dl \hat j$ located at $(0,R,0). Both carry current I. ### An electron enters with a velocity$\overrightarrow{v} =v_0 \hat i$into a cubical region (faces parallel to coordinate plane ) in which there are uniform electric and magnetic fields. The orbit of the electron in front to spiral down inside the cube in plane parallel to the x-y plane . Suggest a configuration of fields$\overrightarrow{E}$and$\overrightarrow{B}$that can lead to it. ### A current carrying loop consists of 3 identical quarter circles of radius R, lying in the positive quadrants of$x-y ,y-z$and$z-x$planes , with their centers at the origin joined together . Find the direction and magnitude to$\overrightarrow{B}$at the origin . ### The magnetic force depends on$\overrightarrow{v}$which depends on the inertial frame of reference . Does then the magnetic force differ from inertia frame to frame ? ### what will the motion of a charged particle in a cyclotron if the frequency of the radio frequency field is doubled ? ### A force that does not work must be velocity dependent force. Is this statement true or false ### The cyclotron frequency$W= \large\frac{eB}{m}$has correct dimension of$[T]^{-1}$. Is this statement true or false ### A changed partice would continue to move with a constant velocity in a region where in , ### A cubical region of space is filled with some uniform electric and magnetic fields . An electron enters the cube magnetic fields. An electron enters the cube across one of its faces with velocity$\overrightarrow {v}$and a position enters via opposite face with velocity -$\overrightarrow v$At this instant . ### Two identical current carrying coaxial loops carry current I in an opposite sense. A simple amperian loop passes through both of them once. Calling the loop as C, ### Consider a wire carrying a steady current , I placed in a uniform magnetic field$ \overrightarrow B\$ perpendicular to its length . Consider the charge inside the wire. It is known that magnetic forces do not work. This implies the

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