Find Current in a Solenoid Given Magnetic Field and Velocity

AI Thread Summary
To find the current in a solenoid given an electron's speed and radius, the magnetic field (B) must first be determined using the relationship between B, charge (q), mass (m), velocity (v), and radius (R). The number of turns per unit length (n) is provided, and it should replace N in the formula for B. The calculation of the total number of turns was incorrect; instead, focus on using n to find B. The centripetal force acting on the electron is equal to the magnetic force, which can help derive the necessary equations. Accurate unit conversion and careful distinction between N and n are crucial for correct results.
elitepro
Messages
5
Reaction score
0

Homework Statement


An electron circles at a speed of 8510 m/s in a
radius of 2.42 cm in a solenoid. The magnetic
field of the solenoid is perpendicular to the
plane of the electron’s path. Find the current in the solenoid if it has
23.3 turns/cm.
Answer in units of mA


Homework Equations


I think you can use B=uIN
I=B/(uN)
u is the universal vacuum permittivity constant, n is the number of turns

The Attempt at a Solution


I already calculated force to be 2e-6.
There are 56.386 turns total because 23.3*2.42
so I got 2e-6/(4pi*10^-7*56.386)=0.02822
so 28.22 mA
I punched this in and it was wrong.
Did I do something weird?
 
Physics news on Phys.org
elitepro said:

Homework Statement


An electron circles at a speed of 8510 m/s in a
radius of 2.42 cm in a solenoid. The magnetic
field of the solenoid is perpendicular to the
plane of the electron’s path. Find the current in the solenoid if it has
23.3 turns/cm.
Answer in units of mA

Homework Equations


I think you can use B=uIN
I=B/(uN)
u is the universal vacuum permittivity constant, n is the number of turns

The Attempt at a Solution


I already calculated force to be 2e-6.
There are 56.386 turns total because 23.3*2.42
so I got 2e-6/(4pi*10^-7*56.386)=0.02822
so 28.22 mA
I punched this in and it was wrong.
Did I do something weird?

1. why calculate the force? your first task is to determine B. what relates B to q, m, v and R, all of which are given to you or known?

2. your calculation of no. of turns does not make sense to me. Your formula for B is correct if you replace N, the number of turns, by n, the no. of turns per unit length. n is also given to you.
Be careful to distinguish between N and n. When you have B you can calculate the current from that formula.

Watch your units!
 
rude man said:
what relates B to q, m, v and R, all of which are given to you or known?
What equation relates these variables? I can't find one that does
 
How about centripetal force in circular motion = magnetic force?
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Calculating magnetic field outside a solenoid
Replies
15
Views
1K
Non-Uniform Magnetic Field Calculations
Replies
9
Views
2K
Understanding self-inductance in a solenoid.
Replies
3
Views
1K
Current in circular wire surrounding infinite solenoid in a circuit
Replies
7
Views
1K
{ help } Calculating the B-field at the center of a solenoid
Replies
1
Views
2K
Calculating Magnetic Field Strength and Force of Eddy Currents in a Solenoid
Replies
49
Views
5K
Electron in a time variable magnetic field
Replies
5
Views
1K
Confusion on the magnitude of magnetic fields
Replies
6
Views
1K
Magnetization of the core of a long solenoid
Replies
5
Views
2K
Calculating Induced EMF in a Larger Solenoid Slipped Over Another Solenoid
Replies
5
Views
2K

Hot Threads

Recent Insights

Back
Top