Motion in Combined Electric and Magnetic Fields – Class 12 | Chapter – 4 | Physics Short Notes Series PDF for NEET & JEE

Motion in Combined Electric: Motion in combined electric field refers to the movement of charged particles under the influence of multiple electric fields. The fields can be uniform or non-uniform, and they can be static or time-varying. The motion of the charged particles is determined by the net electric field acting on them, which is the vector sum of all the individual fields.

Motion in Combined Electric

In some cases, the motion of charged particles in a combined electric field can lead to interesting and useful phenomena, such as electric discharge, electric currents, and electrostatic focusing. These phenomena have many applications in fields like physics, engineering, and technology.

Lorentz Force

• When a moving charge comes under the influence of magnetic and electric fields, it experiences Lorentz force. Lorentz force is a kind of force that can be calculated as the vector sum of forces created by magnetic and electric fields.

• F_net = F_E + F_B
• Fnet = q(E + v x B)
• The below figure shows the representation of the electric field and the magnetic field along with the motion of charge when they are perpendicular to each other.
• When the values of E and B are adjusted such that the magnitude of the two forces are equal, the total force acting on the charge is zero, and the charges will move in the field undeflected.
• When the strength of electric and magnetic fields are varied to get the forces due to electric and magnetic fields to be equal (F_E = F_B), then the charge can move in the field without any deflection.
• F_net = 0
• F_E = F_B
• qE=Bqv
• E=Bv
• v=E/B
• This case is used when charged particles of a certain velocity (E/B) are used to pass through the crossed fields undeflected. This phenomenon is called a velocity selector. It was applied by J. Thomson to evaluate the charge to the mass ratio in 1897.
• Velocity selector is used in mass spectrometers, where charged objects are distinguished as per their charge to mass ratio.

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By Team Learning Mantras