Finding current of circular (toroidal) solenoid

AI Thread Summary
The discussion centers on the ambiguity of the term "circular" in relation to solenoids, as it could refer to either toroidal or cylindrical shapes. The current calculation using the formula B = µ*N*I/2πr yielded 155.6 A, but there is uncertainty about whether the radius used is the major or minor radius of the solenoid. Clarification is provided that the length of 70 cm and 900 turns suggest the length refers to the axis rather than the wire length. The term "circular solenoid" typically describes the cross-section and does not clarify the shape. Overall, the radius is deemed less relevant unless discussing magnetic flux.
Grandpa04
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Homework Statement
A circular solenoid has a magnetic field of 1.4 T. The solenoid has 900 turns, a radius of 2 cm, and a length of 70 cm. What is the current running through the solenoid.
Relevant Equations
B = µ*N*I/2πr
I assumed that the radius is referring to a major R like in the image below.
selenoid1.png

I plugged all the values (except for length) into the equation B = µ*N*I/2πr to get 155.6 A for the current value. I am unsure if this is the correct value or if radius refers to minor r of solenoid, in which case a different equation is used.

mimxrtor.png
 
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Where does it say that it has a toroidal shape?
 
nasu said:
Where does it say that it has a toroidal shape?
Yes, "circular" is ambiguous. Could mean toroidal or cylindrical.
A "length" of 70cm and 900 turns gives less than 1mm per turn, so the length must be along the axis, not the length of wire. If toroidal, that implies a major radius of 70cm/(2π).
 
The expression "circular solenoid" is not uncommon for a cylindrical one. It refers to the cross-section. The radius is not useful unless there is a question about the flux.
 
nasu said:
The expression "circular solenoid" is not uncommon for a cylindrical one. It refers to the cross-section. The radius is not useful unless there is a question about the flux.
Useful to know, thanks.
 
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