Consider the above experimental setup.
Here the source can emit one photon at a time.
The output from the source is sent to a beam splitter which divides it into three possible paths of equal probability.
Splitter 2 further splits the path 3 into two paths of equal probability.
We have...
Thats what I had in my mind. But is it not possible that even before they meet, they have a fully defined state. After they meet they readjust themselves so as to satisfy Bells theorem.
After all, our past is stored in our present memories. So the present memory can be changed so that we...
Can we have a local hidden variable theory explanation for Bells theorem?
The outcomes of the mesurement (measuring the electron spin of an entangled electron pair as Red or Green) can be random initially without any correlation at all.
But by the time we compare the results of the two...
The actual probability of finding the ball in the picked box would be 0.5.
Is it atleast possible to reduce this?
So if we carry out this experiment many number of times we would see that most of the time the ball turns up in the other box and very few times in the box we picked.
Suppose we are given two boxes and we are told that there is a ball in either one of them.
We are free to pickup anyone of the boxes - but only one.
Then we are allowed to measure or check what is in the picked box and the other one.
Normally we would have 50% chance of finding the ball in...
As per the Wheeler Feynman absorber theory, there cannot be electromagnetic radiation
without an emitter and absorber.
If we had only a single electron in the universe then disturbing it (accelerating it) would not produce any radiation since there was nothing to absorb it. Hence it would...
Thanks for clarifying. This seems to indicate that the amount of energy transferred converges to a fixed value as N (no. of turns) tends to infinity.
Is this because the successive turns in the coil are linked to lesser magnetic flux?
You mean to say that there is limit to the energy that can be transferred to the coil between the interval x/c and 2x/c.
Can we not increase the energy transferred initially by increasing the number of turns in the coil. More turns mean more current flowing in the coil.
The point I was trying to make was that the initail energy due to the current induced in the coil is entirely due to the electromagnetic wave.
The kinetic energy of the electromagnet cannot contribute to the induced current, as it does not decrease initailly.
Lets consider the time interval...
So for smaller velocities (compared to c) there should be no noticeable increase in the amount of energy being emitted by the electromagnet whether it is stationary or moving.
So assume that the velocity of the electromagnet involved in the experiment I mentioned earlier (post 56) is small...
The energy in the radiation should be coming from the source driving the electromagnet.
Assume that the electromagnet is powered by a power source - a battery or a charged capacitor.
Now if the electromagnet is moving more and more faster (at a constant velocity) does it mean that the...
The total energy due to the radiation in all directions should be independent of velocity.
Isn't that so? Otherwise an electromagnet moving at a non zero velocity will emit more than an electromagnet at rest. (when they are switched on)
You got me right, Bruce. That was what I was trying to say.
When the electromagnet is switched on, a magnetic field is also set up around it.
At time x/c the effect of this magnetic field reaches the coil. - (since nothing travels faster than light)
Now since the electromagnet is moving...
Yes, I can see that now. Thanks much.
But what if we repeat the original experiment of the magnet and coil by replacing the permanent magnet with this electromagnet.
Initially the electromagnet is turned off. Then it is nudged so that it moves at a constant velocity v.
Now we power on...
I was assuming that the energy in the electric field was constant, but as DaleSpam has pointed out the faster the magnet moves more the energy in the electric field, so this should not be a problem.
Hi Bruce,
Thanks for replying to my queries.
One more thing here, suppose that we replace the magnet with an electromagnet. The current in the electromagnet is controlled by a switch. Also we will remove the coil.(which was originally placed at a distance x)
Initially the electromagnet...
If we consider the Wheeler Feynman absorber theory the response from the coil arrives as advanced waves from the future to the instant when the magnet starts to move.
So this should get rid of the energy conservation problems.
In this case the resistance is felt immediately rather than 2x/c.
The current strength is proportional to the velocity of the magnet. The faster the magnet moves, more is the current.
The energy stored inside the magnetic field is constant. If the current gets energy from the field surrounding the coil, how can it obtain more and more energy from this field...
Since the self inductance effect is very small let's consider only the mutual inductance.
Suppose that the magnet is initially at rest.
It is given a push at time t=t1. Let's assume that the kinetic energy transferred to the magnet due to this push is Ek.
This kinetic energy may decrease...
The energy transfer here should be taking place due to the induction and not through radiation (which even if present should be small and can be neglected as well).
The delay for the magnet to experience resistance due to the current in the coil seems to be
2x/c.
Indeed, If we follow the...
Are these waves real, like normal electromagnetic waves?
If the moving magnet is emitting an electromagnetic wave, it should do so only if the coil is present. Because if there was no coil there would be
nothing to absorb this wave. Also if there is no coil the magnet will not experience...
If the magnet is stationary then the magnetic field around it is constant and so should the energy stored in it.
On accelerating if the energy stored is increasing it is due to the fact that the kinetic energy of the magnet being converted to the energy of the magnetic field.
If we consider the coil to be moving and the magnet stationary, then it is pretty straightforward that the coil will experience resistance instantaneously.This is because the magnetic field is present where the coil is.
Should not this be symmetrical ie it should not matter who is moving...
So what is the actual delay? 0 or (x/c) or (2x/c) ?
If it is x/c there will be no problem with energy.
But the point here is how can the delay be x/c since the resistance is caused by the induced current in the coil and there should be a time gap between the cause and effect since they are...
But if there is a time delay, what happens to the total energy of the system at time x/c after the magnet starts moving.
(x=distance between the magnet and the coil.)
At this point of time we have the magnet which has not experienced resistance and hence has not lost energy and also a...
Hi Andrew,
So will this not amount to a violation of causality. It appears that the moving magnet has knowledge about the events of the future.
We can also assume that there is a switch in the coil which will allow us to turn on/off the current flow.
Now consider the magnet and stationary...
But consider the case when the coil is not present. Surely the moving magnet should not experience resistance then.
According to the Wheeler-Feynman absorber theory radiation resistance is experienced instantaneously because of the advanced waves traveling back from the absorber. This...
What exactly do you mean by the reaction force in this case? Is it the resistance experienced by the magnet and does it feel the reaction instantaneously as it starts to move?
Hi Drakkith,
That is fine. But suppose say the magnet starts moving at instant t=t1.
So the current would be induced in the coil at t=t1+t and the magnet will start experiencing
resistance only at t=t1+2t.
But what about the total energy of the system at time t=t1+t. At this time we have...
"The magnetic field around the wire doesn't just suddenly appear, it progressively grows stronger as the magnet comes closer"
Initially the magnet is at rest. Now there is a certain amount of magnetic flux linking the coil.
But since the flux is constant there is no current induced.
Now...
Consider a magnet moving towards a coil.
We know that the motion of the magnet will induce a current in the coil and the direction of this induced current is to oppose the motion of the magnet.
Now does the magnet experience resistance to its motion immediately as soon as it starts...
Consider the below (figure 1), an electron gun is made to emit electrons one by one through two slits S1 and S2.
There is a screen at the other side and a pair of telescopes (with electron detectors inside them) T1 and T2 trained on the slits S1 and S2 respectively.
We can choose to bring down...