Practical Work in Physics for Use in Schools and Colleges Volume 4; Magnetism and electricity - Softcover
Inhaltsangabe
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. 1899 Excerpt: ...a better method of testing whether the connexions are right is to introduce an approximate resistance from the box of coils, and then to make momentary contact first with one end and then with the other end of the metre wire. The deflexions ought to be in opposite directions. be required in subsequent experiments, (ii) Measure the exact length between the terminals of the bridge of one of the German silver wires, whose resistance, r, was determined in the last experiment. With the screw gauge find the diameter of the uninsulated wire in two or three places, and take the mean as the true diameter. Calculate the sectional area, a (or tr r2), and determine the specific resistance, k, of German silver by substituting for known quantities in k =--(See Equation i.) Repeat for the other wire and compare your results. Wires are said to be joined a) in series if they are connected end to end successively so that the whole current passes through each of them; (b) in multiple or parallel when joined as in Fig. 12. Fig. 12, so that the main current divides and a part goes through each. The equivalent resistance of a system of wires is the resistance of that single wire which can replace the system in the circuit without altering the value of the main current. 5. To prove that the equivalent resistance of wires joined in series is equal to the sum. of their separate resistances. Apparatus. Metre Bridge: two Resistance Coils of about 50 and 80 ohms: a High-resistance Galvanoscope: a Resistance Box of Coils: two Bichromate Cells. Experiment. Measure very carefully, as in Experiment 4, the resistances, r,, rv of each coil separately. Join the coils in series by a clamp, and, as before, measure the combined resistance, r, of the two, and enter your results in the left-hand ...
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