# Electric field generated by solenoid

• quarkyphysicsgirl

#### quarkyphysicsgirl

Homework Statement
"A long solenoid has a radius of 2.08 cm and 1070 turns per meter. Over a certain time interval the current varies with time according to the expression I = 2.80t, where I is in amperes and t is in seconds. Calculate the electric field 4.54 cm from the axis of the solenoid."
Relevant Equations
E=(1/2r)(alpha)R^2(muo)Ioe^-(alpha)t.
The formula we are given is E=(1/2r)(alpha)R^2(muo)Ioe^-(alpha)t.

However, I am struggling to figure out what each of the symbols stands for in the formula...can someone help me out? Like super confused on what alpha is in this case.

Homework Statement:: "A long solenoid has a radius of 2.08 cm and 1070 turns per meter. Over a certain time interval the current varies with time according to the expression I = 2.80t, where I is in amperes and t is in seconds. Calculate the electric field 4.54 cm from the axis of the solenoid."
Relevant Equations:: E=(1/2r)(alpha)R^2(muo)Ioe^-(alpha)t.

The formula we are given is E=(1/2r)(alpha)R^2(muo)Ioe^-(alpha)t.

However, I am struggling to figure out what each of the symbols stands for in the formula...can someone help me out? Like super confused on what alpha is in this case.
Well well, hello @quarkyphysicsgirl, ##\qquad## !​

You are struggling, but I am too ! The variables in the problem statement don't even appear in the formula you were given !
You sure there isn't a huge mixup going on here ?

Not only that, but the problem statement is imposssible: 4.54 cm from the axis ? Where ? In New York or in Cincinnati ?

Back to the drawing board (or to teacher). It may also help to consult your notes and/or textbook.

Finally, PF has a bunch of rules/guidelines -- well worth reading and - as a PS - check out ##\LaTeX##

##\ ##

• berkeman
The formula we are given is E=(1/2r)(alpha)R^2(muo)Ioe^-(alpha)t.

However, I am struggling to figure out what each of the symbols stands for in the formula...can someone help me out? Like super confused on what alpha is in this case.
That formula doesn't apply to this problem.

In this problem, you have a changing current and therefore a changing magnetic field produced by the solenoid. A changing magnetic field induces an electric field. The problem can be solved by a straightforward application of Faraday's law.

Not only that, but the problem statement is imposssible: 4.54 cm from the axis ? Where ? In New York or in Cincinnati ?
4.54 cm from the axis of the solenoid. I'm not sure why you think there's a problem here.

@quarkyphysicsgirl What is the context of this problem? Is it from an introductory physics course? When they say "long solenoid" it is supposed to be an indication that the formula for ideal solenoid is used. The point indicated (4.54 cm) it is outside the solenoid (radius is 2.08 cm) and the magnetic field is ideally zero at this point. As it is at all points outside the solenoid. Something seems to be wrong. Or weird.

• berkeman and BvU
Just because ##\vec B=0## outside the solenoid doesn't mean ##\vec E=0##.