- #1
Erik P
- 33
- 0
Homework Statement
A circle-formed circuit with an area A lies in the (xy)-plane. An electric current I runs clockwise through the circuit (figure 1). An external magnetic field B exerts a torque t = D(3i - 4j) on the circuit, where D is a positive constant, i is the x-axis unit vector and j is the y-axis unit vector.
a.) Determine the circuits magnetic moment u and determine the magnetic field's components Bx and By.
Homework Equations
Right hand rule
\begin{equation}
\mu = IA
\end{equation}
\begin{equation}
\vec{\tau} = \vec{\mu} X \vec{B}
\end{equation}
The Attempt at a Solution
Solved the first part using the right hand rule, the magnetic moment is in the -z axis so we get:
\begin{equation}
\vec{\mu} = -IAk
\end{equation}
For the second part I know what it is supposed to be, but I get something different.
\begin{equation}
B_x = \frac{3}{IA}
\end{equation}
\begin{equation}
B_y = -\frac{4}{IA}
\end{equation}
But those answers are incorrect, the real answers have the 4 and 3 traded around and both are positive, instead of By being negative. Anyone able to tell me why that is? I figure that since 3 is multiplied by the x-axis unit vector that it should then be a part of Bx not By.