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scholio
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Homework Statement
when protons traveling north in a horizontal plane enter a region of uniform magnetic field of 0.8Teslas in the downward direction, they are deflected into a horizontal circle of radius 0.2 meters. what is the magnitude and direction of a uniform electric field applied over the same region of space that will allow the protons to pass through the region undelflected
Homework Equations
radius r = mv/qB where m is mass, v is velocity, q is charge, B is magnetic field
electromagnetic force F = qE + qv X B where X indicates cross product
electric field force F_E = qE where E is electric field
magnetic force F_B = qv X B where B is magnetic field
charge of electron/proton = 1.6*10^-19 coulombs
mass proton m = 1.67*10^-27 kg
The Attempt at a Solution
i used :
since the proton must not be deflected, i assumed electric field force must equal magnetic force so:
qE = qv X B
i then used radius eq, r = mv/qB and solved for v --> v = qBr/m and subbed it in for v to get:
qE = q(qBr/m) X B and solved for E --> E = (qBr/m)Bsin(theta), i have q = 1.6*10^-19 coulombs, B = 0.8 Teslas, r = 0.2 meters, mass m = 1.67*10^-27 kg but what is theta?
is my approach correct?
cheers