00:02
Hi, in the given problem there is a light bulb which is permanently attached to a coil.
00:11
So here this is the rod might be a soft iron rod shown in the figure and there is a coil wound over this rod and a bulk is attached with this coil and this coil.
00:42
And we have to find whether the bulb is in good condition or not.
00:50
So to find it, we wind another coil with the same rod which is having a switch and a battery attached with it.
01:09
So this is coil a, here this is coil b and this is circuit a.
01:26
Now, in the first part, the action which we have to perform in order to check whether this bulb is correct or not.
01:40
So our first action is to close the switch in circuit a, close the switch in circuit a.
01:56
In circuit a as we close this switch so after switching it close the the current will start growing from 0 to its maximum value so the magnetic field lines will start growing the magnetic field lines which are linked with this coil a as this coil will start behaving like a bar magnet and as the magnetic field associated with it will increase so the number of magnetic lines will also increase and as the number of magnetive lines will increase so the magnetic flux linked with the coil b will start increasing as the magnetic flux linked with the coil b will increase it will induce a current in this coil b so if the bulb is good is it it is in good condition it should glow for a short while and if the bulb is not glowing means the bulb is is not in good condition.
03:00
So we can write when we close the switch in circuit a, the current in this circuit starts increasing due to which this coil a starts behaving like a bar magnet in which the magnetic field lines are still increasing.
04:03
Due to increasing electric current.
04:07
So these increasing magnetic field lines will create a magnetic flux passing through coil b and which is increasing means changing.
04:47
So as per faradies loss of electromagnetic induction and emf and hence an electric current will be induced in coil b.
05:22
So if the bulb glows for a short while, it means it is still and if it does not glow, it means it is not good.
06:08
In the second case, if we keep the switch in the circuit a closed for long time...