In the figure below, a charged particle is moving in a uniform magnetic field B

Question

In the figure below, a charged particle is moving in a uniform magnetic field B with a magnitude of 0.1 T pointing into the pages. The particle is either a proton or an electron. It experiences a magnetic force of magnitude 1.6 times 10^-15 N. (You might need the following info: for proton, the charge q = +1.6 times 10^-19 C and mass m_p = 1.67 times 10^-27 kg. The electron has a mass m_c = 9.1 times 10^-31 kg.) (a) Is the particle a proton or an electron? Explain. (b) Determine the particle's speed. (c) Determine the period of the motion. (d) Circle the correct statements below. If the other particle (to that stated in (a)) was present, for the same magnetic field and magnetic force, particle's direction of motion is clockwise/counter-clockwise its speed is larger/smaller/unchanged its radius of motion is larger/smaller/unchanged its period is larger/smaller/unchanged

Explanation / Answer

(a)

the particle is proton

according to right hand rule curl the fingers of right hand from tangent to maneitc field

the magneitc ofrce is directed towards the center

====================

(b)

magnetic force Fb = q*v*b

v = Fb/(qB)

v = 1.6*10^-15/(1.6*10^-19*0.1)

v = 10^5 m/s

===========

(c)

IN magnetic field Fc = Fb

m*v^2/r = q*v*B

r = mv/qB

time period T = 2*pi*r/v

T = 2*pi*m/qB

T = 2*pi*1.6*10^-27/(1.6*10^-19*0.1)

T = 6.3*10^-7 s

===================

clockwise

unchanged

smaller

smaller

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