EM, AC,
KVL does indeed hold.
First, lets look at a few definitions of what KVL is:
1) Electrical Engineering Dictionary - CRC Press, 2000Kirchoff’s voltage law (KVL) a fundamental
law of electricity that states that the
sum of the voltage drops and rises in a closed
loop must equal 0.
2) Fundamentals of Electric Circuits - 3ed. - p.37Kirchhoff’s voltage law (KVL) states that the algebraic sum of all voltages
around a closed path(or loop) is zero.
or alternatively;
Sum of voltage drops = Sum of voltage rises
3) Modern Dictionary of Electronics_7ed - p.408Kirchhoff’s laws- No.2:The algebraic sum of the voltage drops in any closed path in a circuit is equal to the algebraic sum
of the electromotive forces in that path.
4) The Resource Handbook of Electronics - CRC Press, 2001 - sect. 6.2Kirchoff’s voltage law (KVL). The algebraic sum of instantaneous voltages
around a closed loop is zero. **
** In my opinion, this is the best one of the four offered here.
The first observation one should make by examining what professor Lewin has presented along with his objection, is that his explanation of KVL and his use of the law, is incorrect. Applying KVL involves using voltage drops or losses across the circuit elements, but always using the same direction or polarity. Lewin has arbitrarily flipped the voltage meter across one resistor and this accounts for his opposite polarity problem. In fact, the voltage, if assumed to be correctly measured across the resistors, will sum to either +1V or -1V, not -0.1V and +0.9V. That is his error number 1. How could a prestigious college professor mess up something as basic as KVL?
MH, you are on the ball my friend.
The second observation one should make, and this is how Lewin skewed the experiment, is that there are two (or four, depending on the position of points A and D) voltage drops that are not accounted for. The interconnecting wire between the resistors must in fact be included in this KVL computation, as per the above definitions, but they were not, and no one except MH has recognized this.
The sum of the instantaneous voltages around this closed loop do indeed equal zero volts!But you won't get this result if you do not measure all the voltage drops!
See the attached scope shots of all four voltages in the first diagram of my simulation. The sum is 0V.
KVL holds regardless if the emf is induced by induction, or if impressed by a source or emf such as a battery.
@EM, this experiment has nothing to do with induction in the measurement probe cabling or wires. That is a misnomer I'm afraid. @AC, the conventional vs. electron current debate is irrelevant in regards to the results of this experiment. The results are equal either way.
.99
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Topic: Professor Walter Lewin's Non-conservative Fields Experiment (Read 329976 times)
