Magnitude of electric and magnetic fields question. Help,

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Homework Help Overview

The problem involves an ink drop with a specified charge moving through electric and magnetic fields. The objective is to determine the speed at which the electric and magnetic forces acting on the charge are equal, given the magnitudes of the electric field and magnetic field.

Discussion Character

  • Conceptual clarification, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to equate the magnitudes of the electric and magnetic forces using the provided values but encounters an incorrect result. Some participants question the comparison of electric field strength and magnetic force, suggesting a need to clarify the definitions and units involved.

Discussion Status

Participants are actively exploring the relationships between the forces and the fields involved. There is a recognition of potential misunderstandings regarding the units and definitions of force, with hints provided to guide the original poster's reasoning without offering direct solutions.

Contextual Notes

There is an indication that the original poster may have misapplied the relationship between electric field strength and magnetic force, leading to confusion in their calculations. The discussion highlights the importance of understanding the units of measurement in the context of the problem.

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Homework Statement



An ink drop with charge q = 3 ✕ 10-9 C is moving in a region containing both an electric field and a magnetic field. The strength of the electric field is 8E5 N/C and the strength of the magnetic field is 1.3 T. At what speed must the particle be moving perpendicular to the magnetic field so that the magnitudes of the electric and magnetic forces are equal?

Homework Equations


F= q x v x B



The Attempt at a Solution



Right now I know the magnitude of the electric field is 8E5 so I can take that and set it equal to my other numbers... 8 x 10^5 = 3E-9 C x 1.3 T x ( ? M/s)
Solving for m/s, I get 2.05E14 which turns out to be incorrect.
Not sure what i am doing wrong any help would be nice!
 
Physics news on Phys.org
##q \vec{v}\times\vec{B}## gives you the magnetic force on the charge. ##\vec{E}## is the electric field, which is not a force, so you can't compare them directly. What's the force on the charge due to the electric field?
 
Hint: What are the units on the left and right hand sides of your equation, and what should they be?
 
N/C= C x T x m/s. those are my units.. Which I now realize I have done something wrong. Any more help?!
 
At what speed must the particle be moving perpendicular to the magnetic field so that the magnitudes of the electric and magnetic forces are equal?

What's the unit of force?
 

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