Added test for float32 upcast in array_ops

Author: allecole

doc/source/whatsnew/v3.0.0.rst

@@ -752,6 +752,7 @@ Conversion
 - Bug in :meth:`Series.astype` might modify read-only array inplace when casting to a string dtype (:issue:`57212`)
 - Bug in :meth:`Series.convert_dtypes` and :meth:`DataFrame.convert_dtypes` removing timezone information for objects with :class:`ArrowDtype` (:issue:`60237`)
 - Bug in :meth:`Series.reindex` not maintaining ``float32`` type when a ``reindex`` introduces a missing value (:issue:`45857`)
+- Bug in :meth:`_array_ops._maybe_prepare_scalar_for_op` not maintaining ``float32`` type when converting NumPy floating scalars (:issue:`61951`)
 
 Strings
 ^^^^^^^

pandas/tests/series/methods/test_convert_dtypes.py

@@ -318,3 +318,9 @@ def test_convert_dtype_pyarrow_timezone_preserve(self):
         result = ser.convert_dtypes(dtype_backend="pyarrow")
         expected = ser.copy()
         tm.assert_series_equal(result, expected)
+    
+    def test_float32_series_addition_preserves_dtype(self):
+        # GH#61951
+        ser_a = pd.Series(np.zeros(1000000), dtype="float32") + np.float32(1)
+        ser_b = pd.Series(np.zeros(1000001), dtype="float32") + np.float32(1)
+        assert all(dtype == np.float32 for dtype in (ser_a.dtype, ser_b.dtype))