Magnetic Field

In CGS system, the magnetic field is expressed in gauss.
If a charge of moving with a velocity of perpendicular to a uniform magnetic field experiences a force of , then the magnitude of the field is . The SI unit of magnetic field is . Thus,

In CGS systems
1 tesla gauss

Magnetic field region with its initial velocity parallel to the field direction

Direction of velocity of electron is parallel to direction of magnetic field) So, velocity is constant. Hence, there is no change in direction and magnitude of the velocity.

Since, the current through two wires are from left to right, the magnetic field is directed outwards the plane of the paper. Also, current through the other two wires are from right to left, the magnetic field due to them is directed inwards the plane of the paper. Since, the value of current through all the wires is same and point is equidistant from all the wires, the magnitude of magnetic fields are same. Hence, they are cancelled. So, the net magnetic field is zero.