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ch15
electromagnetic machines keywords
| Term | Definition |
|---|---|
| Flux | What 'flows' in the magnetic field. |
| Current turns | What drives the flow of flux in a magnetic circuit. |
| Flux density | Magnetic field strength, how closely packed the field lines are. |
| Faraday's law (in words) | Induced emf proportional to rate of change of flux. |
| Flux linkage | (Flux enclosed by a coil) x (number of turns) |
| Permeance | Measure of how easily flux can flow in a 'magnetic circuit'. |
| B field | Magnetic field |
| symbol for magnetic field strength (or flux density) | B |
| symbol for flux | phi (capital = O with I through it) |
| Flux density = | Flux / area (through which flux 'flows') |
| Magnetically hard | Difficult to magnetise AND stays magnetic for a long time. e.g. steel |
| Magnetically soft | Easy to magnetise AND loses magnetism quickly. e.g. iron |
| Hysteresis | e.g. field that depends on current applied field and on previous field. |
| Field lines indicate... | direction of force (on free north pole) |
| domain | microscopic magnetic space within a magnetic material |
| Field lines show strength ... | from their closeness together (the density of the flux) |
| unit for flux | weber, Wb |
| unit for field strength | tesla, T |
| unit for permeance | Wb A^-1 (weber per amp turn) |
| Flux (analogous to) | current (in an electric circuit) |
| current turns (analogous to) | potential difference (in an electric circuit) |
| permeance (analogous to) | conductance (in an electric circuit) |
| emf proportional to | rate of change of flux |
| emf in direction such that | it opposes change that causes it |
| lines of flux tend to | shorten and straighten |
| iron is laminated to... | reduce eddy currents |
| permeability (analogous to) | conductivity (in an electric circuit) |
| unit for permeability | Wb A^-1 m-1 (weber per amp metre) |
| symbol for permeance | lambda (capital lambda = upside down V) |
| symbol for permability | mu (same as for micro) |
| symbol for current turns | NI |
| unit for current turns | A (amp turns) |
Created by:
allydavies
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