This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 Excerpt: ... 10. A uniform wire is bent into the form of a square: find the resistance between two opposite corners in terms of the resistance of one of the sides. 11. Twelve incandescent lamps are arranged in.parallel between two electric light leads. The difference of potential between the leads is 99 volts, and each lamp takes ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 Excerpt: ... 10. A uniform wire is bent into the form of a square: find the resistance between two opposite corners in terms of the resistance of one of the sides. 11. Twelve incandescent lamps are arranged in.parallel between two electric light leads. The difference of potential between the leads is 99 volts, and each lamp takes a current of 0.75 ampere: what is the equivalent resistance between the leads? Ans. 11 ohms. 12. A battery of 20 ohms resistance is joined up in circuit with a galvanometer of 10 ohms resistance. The galvanometer is then shunted by a wire of the same resistance as its own: compare the currents produced by the battery in the two cases. Ans. C: C = 5: 6. 13. In the preceding example determine the ratio between the currents which flow through the galvanometer before and after it is shunted. 14. How would you arrange a battery of 12 cells, each of 0.6 ohm internal resistance, so as to send the strongest current through an electro-magnet of resistance of 0.7 ohm. 15. In a Wheatstone's bridge (Fig. 356) A = 10 ohms, B = 1,000 ohms, and G = 50 ohms: what is the resistance of D, if the galvanometer shows no current? Ans. 5,000 ohms. CHAPTER VI. ELECTRO-MAGNETISM. 648. The Current's Lines of Magnetic Force.--If a wire, carrying a current of electricity, be passed through a sheet of paper, as indicated in Fig. 359, and if iron filings be sprinkled upon the paper, they will arrange themselves so as to form circles around the wire. If then a short magnetic needle be moved about the wire, it will tend to place itself tangentially to the circle passing through its centre. If the direction of the current be reversed, the needle will turn through 180. The circles of the filings show the paths of magnetic lines of force, which owe their existence to the electr...
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