# If two protons are travelling in same direction parallel to each other, then what would be the nature of force? Attraction or repulsion and why??

### Asked by Pragyashree Jain | 21st Jul, 2014, 10:43: AM

When two protons are travelling parallel to each other, they will repel each other.

We know that when charges/current flows in the same direction in two wires, there is an attractive force between the two.

Hence, there should be magnetic attraction between the protons.

But, if we apply relativity concepts to the scenario, then the protons moving parallel to each other would see each other as stationary charges in their reference frame. Hence, electrostatic repulsion will take over the two and net force on the protons will be repulsive.

### Answered by Romal Bhansali | 21st Jul, 2014, 11:20: AM

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