commutatorn.
/ˈkɒmjuːteɪtə/ 1.
a. He who or that which commutes or exchanges. spec. A contrivance in an electric machine or telegraph instrument for altering the direction or course of the electric current.
ΘΚΠ
the world > matter > physics > electromagnetic radiation > electricity > electrical engineering > operation of machinery > [noun] > regulation of current > device for
inversor1839
break-piece1842
rheotrope1843
break1852
commutator1874
1874 W. R. Grove Experimental Investigations in On Correlation Physical Forces (ed. 6) 253 A commutator might be easily arranged..for effecting the alternation.
1881 Q. Rev. 446 The commutator..used in all direct current machines..was invented in Italy in 1860.
b. An attachment, usually consisting of a ring of copper segments separated by insulating strips, connected with the armature of a dynamo, which, by revolving in contact with the brushes, directs and makes continuous the electric current produced in the armature coils of the machine. Also attributive.
ΘΚΠ
society > occupation and work > equipment > machine > machines which impart power > [adjective] > part of a dynamo
commutator1880
society > occupation and work > equipment > machine > machines which impart power > [noun] > dynamo > parts of
commutator1880
inductor disk1885
rocker1888
inductor-plate1894
the world > matter > physics > electromagnetic radiation > electricity > electrical engineering > armature > [noun] > attachment controlling current
commutator1880
1880 J. W. Urquhart Electr. Light 58 He placed the magnet vertically and revolved the coils about a horizontal axis, and added a commutator to make the currents flow in one direction.
1884 S. P. Thompson Dynamo-electr. Machinery 133 The only other dynamo in which a commutator at all resembling that of the Brush machine is used is Newton's dynamo.
1884 F. Krohn tr. G. Glaser de Cew Magneto- & Dynamo-electr. Machines 228 The commutator am-meter is an aperiodic galvanometer.
1896 S. P. Thompson Dynamo-electr. Machinery (ed. 5) 395 One of these commutator coils.
1902 Encycl. Brit. XXVII. 579/2 The levelling process may evidently be carried still further by the insertion of more coils and more corresponding sectors in the commutator, until the whole armature is covered with winding... A ring and a drum armature, each with eight coils and eight commutator sectors.
1909 Installation News 3 62/1 High speed tends to undue friction and wear of the commutator surface.
1916 Standardization Rules Amer. Inst. Electr. Engin. 47 Brush friction of commutator and collector rings.
1959 Which? Aug. 86/2 Eleven machines had induction motors... The remaining 15 machines had commutator motors.
c. A device effecting the automatic exposure of photographic plates at given intervals during a total eclipse of the sun.
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1897 D. P. Todd in Astrophys. Jrnl. 5 323 The basis of the commutator is an old chronograph with a ten-inch cylinder.
1900 D. P. Todd in Rep. Brit. Assoc. Adv. Sci. 674 The commutator regulated the exposures and recorded their times as well.
2. Algebra.
a. Of the elements a, b of a group, the quantity a–1b–1ab. Also attributive.
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the world > relative properties > number > mathematical number or quantity > numerical arrangement > [noun] > set > in abstract algebra > groups > quantity
commutator1908
1908 H. Hilton Introd. Theory Groups Finite Order i. 4 The commutator of a and b.
1964 W. R. Scott Group Theory iii. 58 [H, K] will denote the subgroup generated by the set of all commutators [h, k] with h ∈ H and k ∈ K... The commutator subgroup..of G is the subgroup [G, G].
b. Of the matrices or operators A, B, the quantity AB—BA. Also attributive.
ΘΚΠ
the world > relative properties > number > mathematical number or quantity > numerical arrangement > [noun] > array > matrix > operation or result of
transposition1858
latent root1883
involutant1890
character1931
commutator1935
trace1938
1935 E. U. Condon & G. H. Shortley Theory Atomic Spectra ii. 25 We shall use the notation [A, B] for the simple commutator A B—B A.
1939 V. Rojansky Introd. Quantum Mech. ix. 326 The matrix αβ—αβ is the commutator of α and β.
1965 L. C. Biedenharn & H. Van Dam Quantum Theory of Angular Momentum 8 By commutator algebra..they derived all the matrix elements for..the complete Racah co-efficient.
This entry has not yet been fully updated (first published 1891; most recently modified version published online December 2019).
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n.1874