Hello every one. This is Jatin again. Today we are going to practically see the impulse response of an RC circuit.
So, here we have an RC circuit. It consists of a resistance of 1 kilo ohms and a capacitance of one microfarad.
These two probes provides the input to the RC circuit and through these two wires we fetch the output out on the oscilloscope.
As an input we give impulses at regular intervals to the RC circuit. You can see these sharp narrow pulses here on your screen.
We know that the impulse response of an RC circuit is an exponentially taking function.
Since we have given impulse as an input to the RC circuit, on the oscilloscope we observe that the output is indeed an exponentially taking function,
showing that if any system is given impulse as an input and the output is the systems impulse response.
Talking about impulses not only in electrical systems but in everyday life like things happening around us, we observe impulse and their impulse responses.
Let's take up some of those examples. So as Jatin has mentioned there are a lot of real life examples of impulses.
I'm Meghasyam, I am going to talk about some of these real life examples now.
So, you have seen a nail and a hammer. So you have a nail
and you have a hammer. So when you, you know, hammer the nail as such, the contact of the nail
and the hammer is just for you know, a few milliseconds but the momentum
or the force that you impact in that few seconds is really large, so you can consider this as an impulse being given to the nail,
and you know, you have seen in the most of the movies the guy gets a heart attack
and then they do a defibrillator and then kick-start the heart.
So let me just talk about this once. You have a battery here, you have a battery
and you have two switches which will connect the battery to a capacitor. There is an inductor
and there is one more switch and then here you have the patient's heart.
So what you do in a defibrillator is, you know, you have the battery then you charge the capacitor
and then you open the switches. Now it's totally charged, now it's starts so
the guy is holding the defibrillator. As soon as he presses it across the heart
and then jumps starts the heart. So what it does is you close the switch it completes the circuit between the capacitor
and the heart and all the energy across this you know, given to the heart as an impulse,
so basically, that's why you call it kick starting the heart.
And let's get to one more example. The other example should be, most of you might have seen your parents
or you know you yourselves must might be having cars. When you switch on the car with a key, so the engine
how it's starts is basically a small spark comes when you switch on the key
and this spark starts the engine and then it's similar with tube lights.
So if you have a tube light with the spark plug so what it does is, it gives a small spark to start the tube light.
That also can be considered as an impulse and let's talk about momentum change now.
Suppose a guy is traveling in a car and he is traveling real fast.
and then I don't know maybe, he didn't watch it but he meets a brick wall, and then you know,
the car just comes to a stop, I mean it's damaged, But say, the car has a mass m
and it's a moving at a velocity v and then as soon as it hits the brick wall, it comes to a stop.
As soon, say the car has a mass m and it's moving with a velocity v and then as soon as the car,
so let's say the car has a mass m and a velocity v, it's moving and then it hits a brick wall.
So the car crashes. But it, you know, it goes from velocity v to 0,
after it crashes its 0 obviously, in a few milliseconds, so the momentum which was first mv is now 0.
So, if the car is moving really fast say at say 60 mph and you know cars weigh,
you know, 2 tonnes or something like that which is 2000 kilos. So the momentum change,
the change of momentum from it's moving, let's say, assume it's moving from a constant speed,
the momentum changed from this to zero and this time here is very very less, milliseconds, you know, less than that.
Because, it just hit a brick wall. Now, if you look at the change of momentum
this would be an impulse, momentum just went from being so high to zero.
How many of you have, you know, just got a shock like or you know, touched the burning pan?
Then you just retrieve your hand back, because the neurons they actually send
the electrical impulse to the brain saying, "Oh, I touched something bad, just get back".
or you know when somebody tries to hit you, you'll like close your face altogether because,
it's kind of an.. you get all these impulses in everyday life. Your body is basically made up of electrical impulses.
So, the signals the body sends you, the touch, the tap, these are all the electrical impulses.
See, your body is made up of electrical impulses.
Impulses practically make a lot of sense but I need to mention this thing, an ideal impulse will not exist practically
because an ideal impulse is infinity at a single point.
So practically, we say impulse is something you know, a signal which has high amount of energy or you know,
not high amount of energy, a signal which has high value in a very less amount of time and impulses can be in many domains.
Now, you've seen impulses in time. How does an impulse in frequency look like?
You'll get to know more about this when we talk about Fourier transform, because a pure sinusoid is an impulse in frequency domain.
So you know, when you talk about impulse ask in which domain, because a spark plug it's an impulse as an input.
But how? Is it impulse in time?
Is it impulse in, you know, heat? So an impulse is basically a signal
which is really high in a really small range of the base unit we're considering.
The base unit can be time, frequency, I mean whatever. So I've given you some examples of impulses
which occur in practical life and impulses are there everywhere, you just have to notice them.
I'd like to see you guys discussing on the forums on what can be impulses and what cannot be impulses.
And thank you very much.