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The Pamphlet Collection of Sir Robert Stout: Volume 50

University of New Zealand. — Chemistry and Experimental Physics. — Paper b. Electricity and Magnetism

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University of New Zealand.

Chemistry and Experimental Physics.

Paper b. Electricity and Magnetism.

1.Describe fully the phenomenon known as the extra-current. How are extra-currents investigated? In what way do they depend upon the resistance of the circuit and on its coefficient of self-induction?
2.Describe the essential parts of some form of continuous-current dynamo-electric machine, and point out the advantages respectively possessed by dynamos that are
(a)separately-excited,
(b)shunt-wound,
(c)series-wound,
(d)compound-wound.
3.What is the use of a condenser? Describe the construction of a standard condenser. How would you ascertain whether a condenser marked "one microfarad" really had that capacity?page 2
4.If a condenser (say of 1 microfarad capacity) is introduced into the line in the circuit of an ordinary Morse telegraph, the signals refuse to pass; yet a telephone can still be heard through the condenser. If a big electromagnet having many turns of wire be introduced into the line in the circuit of an ordinary telephone system, it is found almost impossible to hear through it; speech practically refuses to pass; yet a Morse instrument will work almost as well as before. Explain these things.
5.What is the relation between the strength of an electromagnet, and the number of amperes of current that excite it, and the number of turns of wire in its coil? Give some account of the researches made to ascertain this relation experimentally.
6.Upon what circumstances does the electromotive force of a voltaic cell depend? How are the conflicting chemical and contact theories to be reconciled?
7.Describe the siphon-recorder.
8.Explain in detail the methods adopted for measuring the electric resistances of substances (a) of very low conductivity, (b) of very small resistance.
9.Give an account of the system of units adopted in electrical measurements, grouping them in two sets, electrostatic and electromagnetic.