A magnetic field can deflect a beam of electrons, but it cannot do work on the e

Question

A magnetic field can deflect a beam of electrons, but it cannot do work on the electrons to change their speed. Why? 1. When a magnetic field does work on the electrons, the work is changed into light instead of increasing the energy of electrons. 2. A magnetic field can do work on the electrons. The work can either increase or decrease the speed of the electrons, however, with time-averaging their speeds remain constant. 3. The direction of a magnetic force is always perpendicular to the velocity of an electron. Thus, it cannot do work on the electron. 4. Moving electrons change the magnetic field such that it cannot do work on the electrons.

Explanation / Answer

Answer is :

Option 3 : The direction of a magnetic force is always perpendicular to the velocity of an electron . Thus , it cannot do work on the electron.

Reason : Force on a charged particle in a magnetic field is F= q V x B . Since F is a vector product of velocity vector V and Magnetic field B. It is always perpendicular to the magnetic field. Hence Work done by magnetic field on charged particle is zero

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.