(7) Depends on the respective internal resistances, as well as on E.M.F.s. (8) Ratio is 3 5. (9) 15 64 (10) Either 6 in series, or 3 in series and 2 in parallel. (12) and ampères respectively. E 13 2 E 13 (15) There is no limit. (14) Limit is C = Prove by formula. (21) (i.) 5 ohm; (ii.) from '5 ampère to ‡ ampère; (iii.) volt. •16 (5) (i.) Heat in first case: Heat in second case = E2: E 2: I. (4) 115 lbs. nearly. 3 (ii.) In the first case of the heat is internal and 3 external, while in the second case is internal and external. (6) 4 in series, 2 in parallel; 1.8432 calories per second; 77,414,400 ergs per second. (12) (i.) 90 watts; (ii.) 9.72, 4·86, and 4·86 calories per second respectively; (iii.) 9 watts. CHAPTER XVIII. (1) The needle is unaffected. (4) Consider the equivalent magnetic shell. (5) From E to W. (6) It will vibrate vertically, making and breaking contact alternately. (7) 9'425, nearly. (8) tan 0 = 47.124, nearly. (9) Strength = pt = C. (10) P x I = n C, or p = n C. (11) Let be the common thickness, expressed in centimètres, of coil and = tn C, or p = n C. shell. Then pt (5) (i.) 4 π n C A; (ii.) 4 π × pole-strength = (4π)2 × n C k A. CHAPTER XXI. (2) Consider the earth's field and the magnetisation of the soft iron due to this. (6) This is an example of Lenz's law. (2) Eddy currents arise. CHAPTER XXII. (3) Induction; Lenz's law. (4) By magnetic induction the field due to the magnet is altered. (6) Eddy currents arise, and Lenz's law holds. (7) (i.) Hardly any extra current; (ii.) decided extra current; (iii.) still greater extra current. (8) Slower vibration. Compare with Question 6. (9) Still slower vibration. (10) Observe that with suitable pole downwards the vibrations may even be stopped altogether. CHAPTERS XXIII., XXIV., and XXV. (1) Small internal resistance, low F. M. F. (2) Much depends on whether or no the dynamo can 'leak' to earth. (3) 37.96 kilogram-mètres per second. (4) (i.) 333 ampères; (ii.) 163 ampères, 1666} watts, 3333 watts, 1666 watts; (iii.) 3 ampères, 666 watts, 600 watts. (5) 50 ohms. (6) 892 yards, nearly; '99 okm. INDEX. ACC ACCELERATION, dimensions of, 13 Accumulator, electric current, 366 Activity, unit of, 239. 298 in the voltaic circuit, 240 et seq. - in the circuit of a dynamo and motor, -in cases of induction, 347 et seq. experiments with, 78 Air, its specific inductive capacity taken Alphabet, Morse, 420 Amalgamation of zinc plate in galvanic Amber. earliest observations of its electric Ammeter, or current galvanometer, 291 different kinds of, 443 Ammonium chloride, electrolysis of, 185 Ampère's discovery of the equivalence of a theory of magnetism, 326 Angles, solid, 304, 322 Anions, 184 Anode, 183 Arago's disc and magnetic needle, 363 Arc, electric, 434 appearance of, 439 reverse E.M.F. of, 440 BUN Armatures wound 'for E.M.F.' and 'for Aron, coulomb-meter of, 448 Astatic system of needles for galvano Atmosphere, electrostatic potential at a 'Attracted-disc' electrometer, 153 Attraction and repulsion in magnetism, 2; occurring in magnetic and diamag- Aurora borealis (see references given in Axis, magnetic, definition of, 29 correction for error in the, 33, 36 293 Calorie, unit of heat so called, 239 formulæ for, 142, 146, 148 Carbon plates of constant battery-ccs, 181 Cascade arrangement of Leyden jars, 88 Cavendish's method of finding specific in- Cells [see under Battery-cells, Thermo- Centimètre, the unit of length. 12 tem, 12 sign of, distinguished from sign of 83 residual, 91 bound and free, 81 exemplified by alternate discharge, 'Chemical' theory of voltaic cell, 170 magnetic field due to, 271 et seq. fall of potential through the, 215 Circuits, movement of, general law, 318; magnetic potentials due to, 316, 322 - potential on, due to magnetic field, 317, |