About this video
Electric force is the force between charged particles and is part of the fundamental electromagnetic force. It acts without contact through electric fields, and unlike gravity it can attract (unlike charges) or repel (like charges). It is stronger with more charge, weaker with more distance, and far stronger than gravity, but we rarely notice it because most matter is neutral.
You'll be able to
- explain that electric force acts between charged particles, without contact, via electric fields.
- predict whether two charges attract or repel.
- describe how the amount of charge and the distance affect electric force.
- explain why we don't usually notice electric forces even though they are stronger than gravity.
Key words
- charge
- A property of tiny particles that can be positive or negative and causes electric forces.
- electric force
- The push or pull between charged particles.
- electric field
- A field every charge produces around it; another charge in the field feels a force.
- like charges
- Charges of the same kind (both positive or both negative); they repel.
- unlike charges
- Opposite charges (one positive, one negative); they attract.
- neutral
- Having equal amounts of positive and negative charge, so there is no overall charge.
Transcript
- [Narrator] Check out this cool experiment. I'm bringing a balloon close to a stream of water. See what's going to happen. Whoa, that stream bends. Can you see that? Whoa. What's going on over here? To answer this question, we need to understand electric forces, and that's exactly what we're going to explore in this video.
So we experience a lot of forces in our day-to-day life, like friction, tension, normal forces, gravity, for example. But not all these forces are fundamental. Gravity is a fundamental force. But guess what? The forces like tension and friction, and all of these forces can be clubbed together into one fundamental interaction, one fundamental force, which we call the electromagnetic forces.
And if you look at this carefully, you can see that there are two words, "electro" and "magnetic." The "electro" stands for electric force, and the "magnetic" stands for magnetic force. We combine them together as a single interaction today, but we can study them separately.
So in this video, we're going to study the electric force. So, what exactly is an electric force? Well, if you take any object, any material, like this wooden plank for example, you probably know that it's made up of tiny particles, right? And these tiny particles can have something called charge.
And they are of two kinds of charge. You can have a positive charge and a negative charge. And guess what? Electric force is the force between these charge particles. Charge particles exert a force on each other, which we call electric force. In this particular case, for example, a positive and a negative charge can attract each other.
Now, if we go back to our original experiment, what I did not show at the beginning is that I had rubbed the balloon with a piece of cloth. Because of that, what happened was that charges got accumulated on the surface of this balloon, and those charges were able to put an electric force on the charges present inside the stream of water.
And because of that, there was an attractive force that happened. So if you zoom in over here, we can model it by thinking that there is some negative charges over here, for example, and that was putting an attractive force on the positive charges found in the stream.
And it's that electric force of attraction that caused the stream to bend towards the balloon. Okay, so let's think about the features of this electric force. The first feature you can immediately see is that it's a non-contact force. I didn't have to bring this balloon in contact.
Notice there is a gap between it. So it's a non-contact force. But how does it work? Well, here's how we model it. Every charge produces an electric field around it. And when you have another charge coming in contact with that electric field, it's the field that puts a force on that other charge.
That's how the electric force gets mediated. And if you're wondering, well, yes, even this charge will produce its own electric field. Of course, it'll be in the opposite direction compared to the electric field produce by this charge because it's the opposite charge, like, it's a negative charge.
But don't worry about the direction and stuff. What's important is that every charge will produce an electric field. And because now this charge is in, you know, contact with the electric field, it'll also experience a force. And this should make sense because we have seen that forces come in pair.
Both the charges are going to put an equal and opposite force on each other. So, the electric force gets mediated via electric fields. Okay, next question is, what about the direction of the electric force? Is it always going to be attractive or it can be repulsive as well?
Well, let's see. Sometimes when your body gets rubbed against a blanket or a carpet, you might have noticed the hair standing up like this. What's going on over here, you know? Because of that rubbing, just like with the case of balloon that we saw, charges get accumulated on the surface of your skin and on your hair as well.
And now notice that these hair are standing up, which means they're repelling each other. That's why they're going away from each other, which means electric forces can be repulsive as well. So, unlike gravity, which is always attractive, electric forces can be both attractive and repulsive.
But when would they be attractive and when would they be repulsive? Well, guess what? If you're dealing with unlike charges, they always tend to attract each other. Unlike charges attract each other, opposite charges attract each other. Like charges, on the other hand, will always repel each other.
Okay. So that's about the direction. Now let's think about the strength. What decides the strength of the electric force? Well, one thing that decides it is the amount of charge that is present. If you have a little bit of charge, then the electric force between them would be a little bit.
If you have a lot of charge, you'll have a lot of electric force. So, more charge means a stronger electric force. And again, we can demonstrate this. All right? If you go back to our experiment, over here, I'm rubbing this balloon a lot, so a lot of charge got transferred.
And as a result, look at the amount of deflection that we got on the stream. Okay? Now let's compare it with another experiment in which I'm not going to charge it much. All right? Just charge it a little bit. You saw that. Now look at that. You can still see an electric force but the deflection is much weaker compared to before.
Because there's less charge over here, less electric force. More charge, more electric force. Amazing, right? Okay, the next question we could be having is, if all matter is made of these tiny charge particles, why doesn't every single thing attract and repel each other?
You know, due to electric forces, we don't see that happening. We see gravity, for example, but we don't see electric forces all the time. We have to do these careful experiments. Why is that? Well, that's because almost all matter we have contains an equal amount of positive and negative charges, making it neutral.
And that's why we often do not see electric forces in action. But they're there. Whenever charges do get built up, we do see them in action. And here's the next question. Let's compare electric force with gravitational force. Which one do you think is larger? Just pause the video and think about it.
To answer that question, let's go back to the hair standing. Okay? We know that the entire Earth, the mass of the entire Earth, is pulling down on these hair strands, okay? And look, just a little bit of charge is enough to overcome and repel and go against gravity.
So, a little bit of charge can put enough force to overcome the gravitational force put by the entire Earth. This helps us see that the electric force is stronger than gravity, way, way stronger than gravity. And when you have a lot of charge built up, like during a thunderstorm, whoa, we do really see the power of electric force.
It's the electric forces that causes lightning. Okay, the last thing that decides the strength of the electric force is the distance between the charges. If the charges are very close to each other, the electric force will be very strong. If the charges go farther away, the electric force becomes weaker.
So the electric force decreases with distance. And again, we can see this in action in our experiment. Okay? When I brought the balloon very close, look, the electric force was pretty strong and we could see the strong deflection. If I bring it farther away, look, the electric force has become weaker, and so the deflection has gone down.
Bring it closer, the electric force increases and the deflection increases. Okay, let's put it all together. What we find is that charge particles exert electric forces on each other. It's a part of a much more fundamental electromagnetic interaction. Okay? Light charges will always repel.
Unlike charges will always attract. And then, what decides the strength of that electric force? Well, the amount of charge. More charge means a stronger electric force. And the second thing that matters is the distance. Electric force decreases with distance.
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