A positivelycharged proton is first placed at rest at positi

A positively-charged proton is first placed at rest at position I and then later at position II in a region whose electric potential (voltage) is described by the equipotential lines. Which set of arrows on the left below best describes the relative magnitudes and directions of the electric force exerted on the proton when at position I or II ?

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The figures below represent positively charged particles moving in the same uniform magnetic field.
The field is directed from left to right. All of the particles have the same charge and the same speed v.
Rank these situations according to the magnitudes of the force exerted by the field on the moving
charge, from greatest to least.

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Please some explaintion.....

Solution

part 2 F= q(V X B) so angle between velocity and magnetic field will decide the force in fig 1- angle between V and B is: 90 degree fig 2- angle between V and B is: greater than 90 degree fig 3- angle between V and B is: 0 degree so f= q * V* B * sin(angle) so greates force is: in fig 1 and least in fig 3 so option (d) is correct