Originally Posted by

**thyristor**
Hi!

In my physics textbook there is a problem which reads as follows:

A quadratic wire loop is placed in a homogenous magnetic field of absolute field strength B. The wire is moved to the right (in the picture not shown here), and initially the entire wire loop is inside the field, but after some time time the right edge leaves the field. Will induction in the wire loop occur?

I can easily solve this problem by using Faraday's law of induction. In the initial phase there is no change of flux, hence not voltage induced, according to previously mentioned law. When the right edge of the loop leaves the field however, the area "exposed" to the field will decrease, hence a voltage will be induced by Faraday's law of induction.

However, I also thought of it this way. Consider two metal rods, or pieces of wire, of equal length, placed parallell in a magnetic field and moving with the same speed perpendicularly to the magnetic field. In each rod there will be a voltage induced according to e=vBl, where e is the induced voltage, v is the velocity relative to the field, B is the magnetic flux density and l is the length of the rods.

For the sake of argument, let's say that the lower part of each rod gets negative potential relative to the upper part of same rod. If I now conenct the facing ends of the two parallell rods at both sides, I will connect points of the same potential and thus not change anything. So there still must be a voltage induced, but now we have a wire loop, in which we have already shown, no voltage will be induced.

Could somebody explain what is wrong in my argument, please?