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A-Level H2 物理筆記

Chapter 22: Electromagnetic Induction


Principles of electromagnetic induction
The a.c. generator
Use of cathode-ray oscilloscope
The transformer


(a) Deduce from Faraday’s experiments on electromagnetic induction or other appropriate experiments:
(i) that a changing magnetic field can induce an e.m.f. in a circuit
(ii) that the direction of the induced e.m.f. opposes the change producing it
(iii) the factors affecting the magnitude of the induced e.m.f.

(b) Describe a simple form of a.c. generator (rotating coil or rotating magnet) and the use of slip rings (where needed).

(c) Sketch a graph of voltage output against time for a simple a.c. generator.

(d) Describe the use of a cathode-ray oscilloscope (c.r.o.) to display waveforms and to measure potential differences and short intervals of time (detailed circuits, structure and operation of the c.r.o. are not required).

(e) Interpret c.r.o. displays of waveforms, potential differences and time intervals to solve related problems.

(f) Describe the structure and principle of operation of a simple iron-cored transformer as used for voltage transformations.

(g) Recall and apply the equations VP /VS = NP /NS and VPIP = VSIS to new situations or to solve related problems (for an ideal transformer).

(h) Describe the energy loss in cables and deduce the advantages of high-voltage transmission.

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