Finding current of circular (toroidal) solenoid

[Grandpa04]

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.

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.

 

[nasu]

Where does it say that it has a toroidal shape?

 

[haruspex]

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).

 

[nasu]

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.

 

[haruspex]

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.