Points to ponder:
3. The corner R is a location. So at R the magnetic field due to wire 1,2 and 3 is drawn at R. Add vectorially B1+ B2 + B3 wil give Br. which is same as direction of B2.
3.The B dir is along XY and the current is along X to Y . Hence force is zero as the B and I are parallel to each other.
6. The direction of force should be drawn at the entry point of electron. This will facilitate the investigation on the magnitude of force as it changes with veocity. The electric force does not change with velocity Hence the downward force is geater than the electric force. Therefore the beam of electrons bend downwards.
