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(20%) Problem 4: In a mass spectrometer, a specific velocity can be selected fro

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Question

(20%) Problem 4: In a mass spectrometer, a specific velocity can be selected from a distribution by injecting charged particles between a set of plates with a constant electric field between them and a magnetic field across them (perpendicular to the direction of particle travel). If the fields are tuned exactly right, only particles of a specific velocity will pass through this region undeflected. Consider such a velocity selector in a mass spectrometer with a 0.085 T magnetie field. 50% Part (a) what electric field strength, in volts per meter, is needed to select a speed of 3.9 x 106 m/s? Grade Summ Potential sin0 cos0 cotanOasinacos0 atan0 acotan0 sinhO tan() ? ( Attempts rem (2% per atten detailed view 1 2 3 e Degrees O Radians Submit Hint I give up! Hints: 1 %deduction per hint. Hints remaining: 2 Feedback: deduction per feedback. S8 50% Part (b) what is the voltage, in kilovolts between the plates if they are separated by 115 cm? All content O 2018 Expert TA, LLC

Explanation / Answer

magnetic field = B = 0.085 T

speed = v = 3.9 x 10^6 m/sec

electric force = magnetic force

Ee = B e v

Electric field = E = B* v = 0.085 * 3.9 x 10^6 = 3.315 X 10^5 N/C

B) distance = d = 1.15 cm = 0.0115 m

potential = V = E *d = 3.315 X 10^5 * 0.0115 = 3.81 x 10^3 volts