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Course: Middle school physics - NGSS > Unit 2
Lesson 3: Electric forcesElectric forces
Electric forces, a type of non-contact force, can act on objects without touching. These forces are caused by electric charges in matter. Objects can have positive, negative, or neutral charges. Electric forces can attract or repel, depending on the charges involved. The strength of the force depends on the charge and distance between objects. Created by Khan Academy.
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Like for a cookie 🍪(45 votes)
I got no cookie, I dislike. >:((7 votes)
How do we make two balloons repel each other?(12 votes)
You can make two balloons repel each other by on wool cloth both getting negative charges.(12 votes)
Why are things more prone to static in the wintertime than summer? Summer is more humid...but I thought water conducts electricity. Or is it the heat of the sun that lessens it?(11 votes)
As a Chinese, I have an easy answer for this.
When it's drier, the moisture and sweat on your hand easily jumps from one place to another, creating static. When it's wetter, the charges try to reach their destination but keep bouncing around in the air due to excessive moisture. This change is very significant when you travel from say, Shanghai to Beijing, you need to be very careful of static in Beijing.(10 votes)
When it comes to static electricity, the charge distribution between different materials can vary based on their properties. The ability of a material to gain or lose electrons during contact and rubbing plays a role in determining the charge distribution.
In the case of socks and shirts, it's important to consider the materials they are made of. Socks are often made of materials like wool or synthetic fibers, which have a higher tendency to gain or accumulate electrons when rubbed against certain surfaces. These materials can become negatively charged as they gain excess electrons.
On the other hand, shirts are typically made of materials like cotton or polyester, which have a lower tendency to gain or lose electrons. They are less likely to accumulate excess charges and may retain a more balanced or slightly positive charge.
So, when socks rub against a surface, they may pick up electrons and become negatively charged, while the shirt, with its different material composition, may not gain or lose as many electrons and retains a relatively neutral or slightly positive charge.
It's important to note that the specific charge distribution can also depend on various factors such as humidity, friction, and the materials involved. Therefore, the charge distribution between socks and shirts can vary in different circumstances.(8 votes)
- could a normal ballon pop another normal ballon with nothing on it(5 votes)
- Under normal circumstances, a normal balloon would not be able to pop another normal balloon without anything on it. This is because the force exerted by a regular inflated balloon is not typically strong enough to burst another balloon.
However, if the balloons are subjected to additional forces or conditions that increase the pressure or introduce sharp objects, it is possible for one balloon to pop another. For example, if one balloon is filled with a significant amount of air or if external pressure is applied to it, it may have enough force to burst a second balloon.
In general, though, two normal balloons without any additional factors would not pop each other.(3 votes)
Haha.... Silly socks stuck on silly shirts! Good one.(5 votes)- How come socks get more electrical charges, while the shirt is still positively charged?(4 votes)
not exacly because the martireal on socks are no electrical conductive(1 vote)
- what will happen if both of the objects have neutral charges(2 votes)
Then there is no electric force between the objects.(6 votes)
- Hello I have a question about negative and positive charges. What were to happen if a neutral charge met with another neutral charge, would they repel? And what if a neutral charge were to meet with a negative or positive charge, with they attract?ಠ_ಠThank you for the help whoever responds.^.^(4 votes)
Because neutral charges have zero charge, nothing will happen. When a neutral charge meets a positive or negative charge, they will attract.(2 votes)
- Not 'repulsive force', repelling force.(1 vote)
There is no difference. "repulsive" and "repelling" mean the same thing.(7 votes)
Video transcript
- Have you ever taken
a shirt out of a dryer and found a sock stuck to it? If you have, you might have noticed that once you pull the sock off it was still attracted to the shirt even when they weren't touching. What is even happening here? Well, it turns out
there's an electric force between the shirt and the sock. Electric forces are a
type of non-contact force, which means they can act on objects that aren't even touching. If you've ever noticed two
balloons repelling each other, or if you've ever noticed your hair sticking to something like
a balloon or a sweater, that's what I'm talking about. But why is there an electric force between the shirt and the sock after
they're taken out of the dryer? Well, it turns out that
electric forces are caused by a property of matter
called electric charge. Matter is made up of tiny
particles that can have positive, negative, or neutral charge. Neutral just means that the
electric charge is zero, not positive or negative. When you add up all these
charges most objects tend to have a net charge
that is about neutral. Otherwise we'd be attracted
to all sorts of things, just like that sock. However, an object's charge can change. So in the dryer all that heat and movement allowed some negative
charges from the shirt to move to the sock. Now, when you try to separate the two, they're both electrically charged and there's an electric
force between them. So now that we know what
causes an electric force, let's look at what affects
its direction and strength. An electric force can
attract or repel an object. But how do you know if an electric force will be attractive or repulsive? Well, as the saying
goes, opposites attract. An object with a negative electric charge will be attracted to a
positively charged object. If the second object is
also negatively charged, well, the two objects will
experience a repulsive force and be repelled from each other. So in order to have the sock and the shirt attracted to each other they
must have opposite net charges because they're experiencing
an attractive electric force. What about the strength
of that electric force? Strength will depend
on a couple of factors. First, the charge of each object is proportional to the force. The stronger the charges, the
stronger the electric force. So the greater the electric charge, the greater the electric force. Another factor, how far apart the objects are from each other. The electric force will weaken
as the distance increases. So the force decreases as
our distance increases. As you move the sock away from the shirt eventually the attraction
between them is so weak that we don't even notice it. So the next time you find
yourself doing laundry and having to pull a sock off of a shirt, just remember invisible
electric forces are to blame.