An electron enters a uniform magnetic field B

Esteban Azofeifa

Esteban Azofeifa

Answered question

2022-08-19

An electron enters a uniform magnetic field B = 0.23 T at an angle of 45° to the magnetic field (see accompanying figure). Determine the radius r and the pitch p (distance between loops) of the electron's helical path, assuming its speed is 3.0 x 106 m/s.

Answer & Explanation

user_27qwe

user_27qwe

Skilled2023-05-24Added 375 answers

Given information:
Magnetic field, B=0.23T
Angle between the velocity and magnetic field, θ=45
Speed of the electron, v=3.0×106m/s
First, let's find the radius, r, of the electron's helical path. In circular motion, the Lorentz force is responsible for the centripetal force acting on the charged particle.
The Lorentz force, F, can be expressed as:
F=q(v×B)
where q is the charge of the electron, v is the velocity of the electron, and B is the magnetic field.
The centripetal force, Fc, is given by:
Fc=mv2r
where m is the mass of the electron and r is the radius of the helical path.
Setting F=Fc, we have:
q(v×B)=mv2r
Since the angle between v and B is 45, we can write v×B as:
v×B=vBsin(45)
Substituting this into the equation, we get:
q(vBsin(45))=mv2r
Simplifying, we find:
r=mvqBsin(45)
Substituting the given values into the equation:
m=9.1×1031kg
v=3.0×106m/s
q=1.6×1019C
B=0.23T
we can calculate the radius r:
r=(9.1×1031kg)(3.0×106m/s)(1.6×1019C)(0.23T)(sin(45))
Calculating this expression, we find:
r3.14×103m
Therefore, the radius of the electron's helical path is approximately 3.14×103 meters.
Next, let's find the pitch, p, of the electron's helical path. The pitch is the distance between successive loops along the helical path.
The pitch p can be calculated using the formula:
p=2πrsin(θ)
Substituting the given values into the equation:
r=3.14×103m
θ=45
we can calculate the pitch p:
p=2π(3.14×103m)sin(45)
Calculating this expression, we find:
p0.0089m
Therefore, the pitch of the electron's helical path is approximately 0.0089 meters.

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