uniˈpolar, a. (and n.)
[See uni- and polar a. Cf. F. unipolaire.]
1. Electr. a. Produced by, proceeding from, one magnetic pole; exhibiting one kind of polarity. unipolar induction: electrical induction in which a continuous direct current is produced in a conductor joining a magnetic pole and equator by the rotation of either the conductor or the magnet. Cf. homopolar a. 2.
| 1812 Sir H. Davy Chem. Philos. 168 There are substances that are imperfect conductors which are capable of receiving only one kind of electricity..and which M. Ehrman..has named unipolar bodies. 1873 J. C. Maxwell Electr. & Magn. II. 7 The property produced by magnetism in transparent bodies of twisting the plane of polarization of the incident light, is, like magnetism itself, a unipolar property. 1881 Nature XXIII. 616 To illustrate unipolar conductivity. Ibid. XXIV. 570 Whether it be not possible entirely to separate one from the other, and to produce what may be called a unipolar discharge. 1884 S. P. Thompson Dynamo-Electric Machinery ix. 176 The same fundamental idea has been worked upon by Messrs. Siemens and Halske, who have produced a so-called ‘unipolar’ machine. [Note] This sounds like a lucus a non lucendo, for the machine has two poles. But the name is derived from the term ‘unipolar induction’, which Continental electricians give to the induction of currents by a process of ‘continuous cutting’. 1888 Encycl. Brit. XXIII. 330/1 The so-called ‘unipolar’ induction supposed to be due to the rotation of the earth. 1982 Astrophysical Jrnl. CCLXII. 87 A potential drop ∼1019 volts is generated by the unipolar induction of a rotating accretion disk surrounding the black hole. |
b. Of apparatus: Having, or operating by means of, one magnetic pole; involving, or operating by means of, unipolar induction. Also ellipt.
| 1876 Nature XIV. 263/2 A unipolar magnetic needle. Ibid., The space through which a subsidiary magnet must be moved in order to restore the unipolar to its original position. 1883 Daily News 10 Sept. 2/2 The remarkable machine of Messrs. Siemens and Halske, called the unipolar machine. 1884 Health Exhib. Catal. 79/2 A true unipolar continuous current dynamo. 1884 [see prec. sense]. 1920 Whittaker's Electr. Engineer's Pocket-bk. (ed. 4) 139 Unipolar machines have not been able to compete with heteropolar types. 1940, 1973 [see inductor 3 b]. 1975 Nature 6 Feb. 416/2 The satellite Io acts as a unipolar inductor and a source of constant e.m.f. across the Io flux tube as it moves through the Jupiter magnetic field. 1975 A. Shadowitz Electromagnetic Field xi. 410 A unipolar generator (or motor) differs from a homopolar generator (or motor) in that the rotating disk or cylinder is also a uniform magnet. |
2. Biol. a. Of nerve-cells: Having one pole or fibrous prolongation; connected to the nerve-fibre by a single fibrous process.
| 1859 Todd's Cycl. Anat. V. 436/2 Those [ganglionic corpuscles] from which one tube proceeds are termed unipolar. 1873 A. Flint Physiol. Man, Nerv. Syst. i. 46 Unipolar cells exist in some of the lower orders of animals. 1880 Bastian Brain ii. 48 Unipolar nerve cells..are alleged to exist in the ganglia on the spinal nerves and elsewhere. |
b. (See quot.)
| 1878 F. J. Bell tr. Gegenbaur's Comp. Anat. 597 If the rete remains broken up, then it is known as a diffuse, unipolar, or monocentric rete mirabile. |
3. Electronics. Of a transistor or similar device: involving conduction by charge carriers of a single polarity.
| 1952 W. Shockley in Proc. IRE XL. 1313/1 In order to distinguish between the more conventional transistors and the analog types, we propose to use the words bipolar and unipolar. Ibid. 1365/2 In a ‘field-effect’ transistor, the current flow is carried by one type of carrier only... For this reason the name ‘unipolar transistors’ is proposed. 1973 Sci. Amer. Aug. 48/2 Most integrated circuits produced in the 1960's were of the bipolar type, but production of the newer unipolar type is growing rapidly. 1981 J. C. Sprott Introd. Mod. Electronics viii. 169 The bipolar transistor is so named because current is carried simultaneously by charges of both polarities (electrons and holes) rather than by a single species, as in the FET which is an example of a unipolar device. |
4. Psychol. Of a psychiatric disorder: characterized by depressive but not manic episodes.
| 1965 Acta Psychiatrica Scandinavica Suppl. No. 180. 87 We..have assumed that ‘middle age depressions’ according to Stenbäck and ‘unipolar depressions’ according to Leonhard are merely different terms, which..cover the same nosographic entity. 1982 Donlon & Rockwell Psychiatric Disorders v. 76 Unipolar disorders are much more common than bipolar. |
Hence ˌunipoˈlarity, the condition or character of being unipolar. (Cf. F. unipolarité.)
| 1888 Philos. Mag. Ser. v. XXVI. 129 We do not believe that Ohm ever observed the phenomenon of unipolarity in strong sulphuric acid with [etc.]. |
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Add: uniˈpolarly adv.
| 1906 Jrnl. Physiol. XXXIV. 30 Double induction shocks at a rate of 25 per sec. were used throughout and delivered unipolarly by an entomological pin-point lightly inserted. 1982 Psychiatry Res. VII. 245 Unipolarly depressed patients with higher levels of platelet MAO [sc. monoamine oxidase] activity woke up earlier in the morning than they had before becoming depressed. |