Several magnetic and non-magnetic bars of equal dimensions are glued together as shown on the left. If blue denotes magnetic north, red denotes magnetic south, and grey denotes non-magnetic material, what will be the configuration of the faces on the other end?
Show Hint
For magnetic-bar configuration problems:
\begin{itemize}
\item Track each bar individually through the solid,
\item Remember that flipping reverses magnetic poles,
\item Non-magnetic segments act as fixed references.
\end{itemize}
Step 1: Each bar has uniform polarity along its length. This means the arrangement of magnetic north (blue), magnetic south (red), and non-magnetic (grey) segments remains consistent from one end of a bar to the other, except for reversal due to orientation.
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Step 2: Carefully trace each bar from the visible (left) face to the hidden (right) face, noting:
\begin{itemize}
\item Magnetic bars preserve polarity along their length,
\item Bars that are flipped will show reversed colours on the opposite face,
\item Grey (non-magnetic) segments remain unchanged.
\end{itemize}
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Step 3: Combine the end-face colours of all bars according to their relative positions and orientations as glued.
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Step 4: Compare the resulting configuration with the given options:
\begin{itemize}
\item Options A, C, D: At least one bar shows an incorrect polarity or misplaced non-magnetic segment.
\item B: Correctly represents all magnetic polarities and non-magnetic segments on the opposite face — valid.
\end{itemize}
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Final Answer:
\[
\boxed{B}
\]
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