Hf' 31 Induksie en induktansie transperant 1

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• Hoofstuk 31
• Induksie en Induktansie
• DOELWITTE
• Faraday se wet van induksie (em)
• B-velde ? elektriese velde
• Lenz se wet
• Bewegings emk
• Geinduseerde elektriese velde
• Induktors
• self-induksie
• wederkeurige induksie
• RL stroombane
• Energie gestoor in B-velde

Hoofstuk 30 elektriese stroom ? B-velde
Wat is n elektromotoriese krag (emk)? Bron van
energie ie. n Gewone battery wat n potensiaal
verskil tussen twee punte in n stroombaan lewer.
Ander voorbeelde son selle, brandstof selle,
menslike hart

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31-3 Faraday se wet van induktansie
Wet van induktansie 1831 (Faraday -
Engeland) (Henry - USA)
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Probleem voorbeeld 31-1 - belangrik
Toetspunt 1
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31-4 Lenz se Wet
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Probleem voorbeelde 31-2 en 31-3 - belangrik
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31-5 Induksie en Energie oordrag Bewegings emk
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Bewegings emk verg.
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Probleem voorbeeld 31-4 (a) Plot die vloed deur
die winding as n funksie van x (b) Plot die
geindeuseerde emk as n funksie van die posisie
van die winding, toon die rigtings van die
geinduseerde emk aan (c) Plot die tempo van
termiese energie produksie in die winding as n
funksie van die posisie van die winding
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(b) Plot die geinduseerde emk as n funksie van
posisie van die winding, toon die rigtings van
die geinduseerde emk
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(c) Plot die tempo van termiese energie produksie
in die winding as n funksie van posisie van die
winding.

• Toetspunt 3
• maksimum grootte van emk
• kant wat die B-veld sny

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31-7 Induktors en Induktansie Induktansie
Faraday se wet veronderstel dat n veranderende
magnetiese vloed deur n stroombaan n
geinduseerde emk in die stroombaan veroorsaak.
In die spesiale geval waar die veranderende vloed
self deur n veranderende stroom in die
stroombaan veroorsaak word, praat ons van die
induktansie in die stroombaan.
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Induktansie - SolenoÏde (ideaal)
Magnetiese vloed verbinding N?
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31-9 RL Stroombaan
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31-10 Energie gestoor in n magneetveld
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Chapter 31, Tutorial 3  
2E. A small loop of area A is inside of, and has
its axis in the same direction as, a long
solenoid of n turns per unit length and current
i. If i i0 sin wt, find the emf in the
loop.   Solution 14P. An elastic conducting
material is stretched into a circular loop of
12.0 cm radius. It is placed with its plane
perpendicular to a uniform 0.800 T magnetic
field. When released, the radius of the loop
starts to shrink at an instantaneous rate of 75.0
cm/s. What emf is induced in the loop at that
instant?   Solution   31E. A loop antenna
of area A and resistance R is perpendicular to a
uniform magnetic field B. The field drops
linearly to zero in a time interval of ?t. Find
and expression for the total thermal energy
dissipated in the loop.   Solution  
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33E. A metal rod is forced to move with constant
velocity v along two parallel metal rails,
connected with a strip of metal at one end, as
shown in figure 1. A magnetic field B 0.350 T
points out of the page. (a) If the rails are
separated by 25.0 cm and the speed of the rod is
55.0 cm/s, what emf is generated? (b) If the rod
has a resistance of 18.0 ?, and the rails and
connector have negligible resistance, what is the
current in the rod? (c) At what rate is energy
being transferred to thermal energy? Solutio
n (a) The flux changes because the area bounded
by the rod and rails increases as the rod moves.
Suppose that at some instance the rod is a
distance x from the right hand end of the rails
and has speed v. Then the flux through the area
is ?B BA BLx, where L is the distance between
the rails. According to Faradays law the
magnitude of the emf induced is ? d?B /dt
BL(dx/dt) BLv (0.350 T)(0.250 m)(0.550 m/s)
4.81x10-2 V.   (b) Use Ohms law. If R is the
resistance of the rod then the current in the rod
is I ?/R (4.81x10-2 V)/(18.0 ?) 2.67x10-3
A.   (c) The rate at which thermal energy is
generated is
Figure 1
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36P. Two straight conducting rails form a right
angle where their ends are joined. A conducting
bar in contact with the rails starts at the
vertex at time t 0 and moves with constant
velocity of 5.20 m/s along them, as shown in
figure 2. A 0.350 T magnetic field points out of
the page. Calculate (a) the flux through the
triangle formed by the rails and the bar at t
3.00 s and (b) the emf around the triangle at
that time. (c) If we write the emf as ? atn,
where a and n are constants, what is the value of
n?
Figure 2
             Solution (a)At time t the area of
the closed triangle loop is A(t) ½(vt)(2vt)
v2t2. Thus   (b)   (c) From part (b)
above we see that ? ?2Bv2t ? t1. Thus n
1.
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