A circular conducting ring of radius rotates with constant angular vel...
Induction in a Rotating Conducting Ring
When a conducting ring rotates in a magnetic field, an electromotive force (EMF) is induced due to the motion of the charges within the ring. Let's analyze the scenario:
Setup Description
- A circular conducting ring of radius \( r \) rotates about its diameter (x-axis) with a constant angular velocity \( \Omega \).
- A uniform magnetic field \( \vec{B} \) is applied along the z-axis.
- At time \( t = 0 \), the ring lies entirely in the xy-plane.
Magnetic Flux and Rotation
- The magnetic flux \( \Phi \) through the ring is given by:
\[
\Phi = B \cdot A
\]
where \( A \) is the area of the ring. For a circular ring, \( A = \pi r^2 \).
- As the ring rotates, the area vector \( \vec{A} \) changes its orientation, leading to a variation in magnetic flux.
Induced EMF Calculation
- According to Faraday's law of electromagnetic induction, the induced EMF \( \mathcal{E} \) in the ring is given by the rate of change of magnetic flux:
\[
\mathcal{E} = -\frac{d\Phi}{dt}
\]
- The area vector \( \vec{A} \) can be expressed as \( A \cos(\theta(t)) \), where \( \theta(t) = \Omega t \). Thus:
\[
\Phi(t) = B \cdot \pi r^2 \cos(\Omega t)
\]
- Taking the derivative:
\[
\frac{d\Phi}{dt} = -B \cdot \pi r^2 \Omega \sin(\Omega t)
\]
- Therefore, the induced EMF becomes:
\[
\mathcal{E} = B \cdot \pi r^2 \Omega \sin(\Omega t)
\]
Conclusion
The induced EMF in the rotating conducting ring is sinusoidal, with a maximum value of \( B \cdot \pi r^2 \Omega \) occurring when \( \sin(\Omega t) = 1 \). This phenomenon exemplifies the principles of electromagnetic induction in a rotating system within a magnetic field.