Two parallel plate electrodes are 4.8 cm long with a plate separation of 1 cm. A

Question

Two parallel plate electrodes are 4.8 cm long with a plate separation of 1 cm. A stream of protons enters the region of the plates from one end, an equal distance from both the top and bottom electrodes. A voltage of 480 V across the electrodes deflects the protons so that they just strike the outer edge of the bottom electrode. If a magnetic field is now applied, in addition to the electric field, the deflection of the protons can be reduced to zero and the protons can follow a straight path right through the middle of the plates. What magnetic field strength will allow the protons to pass through the region undeflected while the 480 V potential difference is applied?

Explanation / Answer

y = 1/2 = 0.5cm = 0.005 m

ay = Eq/m = dV*q/dm = (480*1.6e-19)/(0.01*9.1e-31)

along horizantal x = v*t =======> t = x/v

along vertical y = 0.5*ay*t^2

y = 0.5*ay*x^2/v^2

v^2 = 0.5*ay*x^2/y = (0.5*8.43e15*0.048*0.048)/0.005

v = 4.41e7 m/s

Fe = Fb

E*q = q*v*B

B = E/v = dV/vd = 480/(4.41e7*0.01) = 1.088e-3 T <--answer

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

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