My Math Forum  

Go Back   My Math Forum > Science Forums > Physics

Physics Physics Forum

LinkBack Thread Tools Display Modes
February 18th, 2011, 10:21 AM   #1
Senior Member
Joined: Oct 2009

Posts: 895
Thanks: 1

Compare the magnetic field strength inside & outside the so

1 - Compare the magnetic field strength inside and outside the solenoid ?
2 - A magnetic field inside a solenoid is 0.2 T. what is the number of turns/cm of the solenoid if the solenoid carries a current of 10 A ?
3 - The magnetic field a distance of 4 cm from a long straight current - carrying wire is 2 X 10 ^ -5 T . what is the current in the wire ? what is the magnetic field at distance of 12 cm from the wire ?
r-soy is offline  
February 18th, 2011, 11:59 AM   #2
Senior Member
MarkFL's Avatar
Joined: Jul 2010
From: St. Augustine, FL., U.S.A.'s oldest city

Posts: 12,193
Thanks: 504

Math Focus: Calculus/ODEs
Re: Compare the magnetic field strength inside & outside the

1.) If we assume the case of an ideal solenoid, i.e., the turns are closely spaced and the length is long compared to the radius, then we can assume the magnetic field inside is uniform and the field outside is zero. The uniform field strength inside will be given by:


is a constant called the permeability of free space
is the number of turns per unit length
is the current

2.) Using the expression above, we find:

3.) The magnetic field strength outside a long straight current-carrying wire is given by:

where r is the distance from the center of the wire's cross section. Using the data given, we have:

To find the field strength at 12 cm, we may use the fact that the field strength varies inversely as r, so if we triple the distance, the field strength is 1/3 the original.
MarkFL is online now  

  My Math Forum > Science Forums > Physics

compare, field, inside, magnetic, strength

Search tags for this page
Click on a term to search for related topics.
Thread Tools
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
Charge in a magnetic field and a electrostatic problem Raphael Physics 0 May 1st, 2012 12:23 PM
Moving proton, Magnetic field, velocity, force FishFace Physics 3 October 27th, 2011 06:39 AM
How can a changing magnetic field induce an electric current r-soy Physics 1 March 7th, 2011 09:14 AM
Type the four points about how magnetic field is created r-soy Physics 3 February 6th, 2011 10:15 AM
field strength axelle Physics 1 February 9th, 2008 08:24 PM

Copyright © 2018 My Math Forum. All rights reserved.