# Electron Motion in a Long Solenoid

• jehan60188
In summary, the conversation discusses a long solenoid with 100 turns/cm and carrying a current i, where an electron moves in a circle with a radius of 0.022 cm and a speed of 0.048c. The equations used to solve for the current include f = m*v^2/r = q*v*B, B of a solenoid = u*n*I, and I = mv/(r*q*u*n). There was a discrepancy in the final answer, which was resolved by using the correct value for the mass of the particle involved.
jehan60188

## Homework Statement

A long solenoid has 100 turns/cm and carries a current i. An electron moves within the solenoid in a circle of radius 0.022 cm perpendicular to the axis of the solenoid. The speed of the electron is 0.048c (c is the speed of light).

## Homework Equations

f = m*v^2/r = q*v*B
B of a solenoid = u*n*I
where n = number of turns per meter
u = 4*pi*10^7

## The Attempt at a Solution

so B = mv/(r*q) = u*n*I
I = mv/(r*q*u*n)
I = 5436.9 is not correct

your working looks fine to me... But I got a different value for the current when I plugged the numbers in. Maybe that's where the problem is.

I was using the mass of a proton instead of an electron. replugged the numbers, and it works now!
thanks!

## 1. How does an electron move in a long solenoid?

Electrons move in a long solenoid due to the presence of a magnetic field. When a current is passed through the solenoid, it creates a magnetic field that exerts a force on the electrons, causing them to move in a circular path around the solenoid.

## 2. What is the direction of electron motion in a long solenoid?

The direction of electron motion in a long solenoid is perpendicular to both the direction of the current and the direction of the magnetic field. This is known as the right-hand rule, where the thumb represents the direction of the current, the fingers represent the direction of the magnetic field, and the palm represents the direction of the electron motion.

## 3. Does the speed of the electron change in a long solenoid?

Yes, the speed of the electron changes in a long solenoid due to the magnetic force exerted on it. As the electron moves in a circular path, it experiences a centripetal force that keeps it in motion. This results in a constant change in velocity, but the speed remains the same.

## 4. How does the number of turns in a solenoid affect electron motion?

The number of turns in a solenoid affects the strength of the magnetic field. As the number of turns increases, the magnetic field also increases, resulting in a stronger force on the electrons. This causes the electrons to move in a tighter, faster circular path.

## 5. What is the relationship between the strength of the magnetic field and the radius of electron motion in a long solenoid?

The strength of the magnetic field is directly proportional to the radius of electron motion in a long solenoid. This means that as the magnetic field increases, the radius of the electron's circular path also increases. This relationship is described by the equation F=qvB, where F is the magnetic force, q is the charge of the electron, v is the velocity, and B is the magnetic field strength.

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