A 0.210-kg metal rod carrying a current of 11.0 A glides on two horizontal rails 0.490 m apart. If the coefficient of kinetic friction between the rod and rails is 0.200, what vertical magnetic field is required to keep the rod moving at a constant speed?

The  magnetic field is  

Explanation:

From the question we are told that  

    The mass of the metal is  

     The current is  

      The distance between the rail(length of the rod ) is  

      The coefficient of kinetic friction is  

Generally the magnetic force is mathematically represented as

Given that the rod is moving at a constant velocity, it

=>    

Where is the kinetic frictional force which is mathematically represented as

So

=>  

substituting values

=>  

=>  

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