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Middle school physics - NGSS
Course: Middle school physics - NGSS > Unit 2
Lesson 2: Electric forcesElectric forces
NGSS.MS:
MS‑PS2‑3
, MS‑PS2.B.1
, MS‑PS2.B
Electric forces can be attractive or repulsive depending on the types of charges involved. The strength of an electric force depends on the size, or magnitude, of the charges and the distance between them. Learn about how charges interact to create the electric forces that are all around us. Created by Khan Academy.
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How do we make two balloons repel each other?(6 votes)
You can make two balloons repel each other by on wool cloth both getting negative charges.(6 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?(6 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.(4 votes)
could a normal ballon pop another normal ballon with nothing on it(4 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)
- How come socks get more electrical charges, while the shirt is still positively charged?(4 votes)
- make some fiction with the sock and shirt, this can increase it(2 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.(3 votes)
- what will happen if both of the objects have neutral charges(2 votes)
Then there is no electric force between the objects.(4 votes)
- what is a electric charge(3 votes)
Electric charge is the physical property of matter that causes matter to experience a force when placed in an electromagnetic field. Electric charge can be positive or negative (commonly carried by protons and electrons respectively, by convention). Like charges repel each other and unlike charges attract each other. An object with an absence of net charge is referred to as neutral. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that do not require consideration of quantum effects.
=)(2 votes)
- Difference between electric force and electrostatic force?(3 votes)
- The electric force and the electrostatic force are related but have slightly different meanings.
Electric force refers to the force of attraction or repulsion between charged objects. It can act over a distance and is caused by the interaction of electric charges. Electric force can exist between charged objects regardless of whether they are at rest or in motion. For example, the electric force between two charged particles can cause them to attract or repel each other.
On the other hand, electrostatic force specifically refers to the static or stationary electric force between charged objects that are not in motion relative to each other. It is the electric force that exists when charges are not moving or changing. Electrostatic force is responsible for many everyday phenomena, such as the attraction between a charged comb and small pieces of paper or the repulsion between two like-charged balloons.
So, while electric force is a more general term that encompasses all types of forces between charged objects, electrostatic force specifically refers to the static, non-moving electric force between charged objects.(2 votes)
- Not 'repulsive force', repelling force.(1 vote)
There is no difference. "repulsive" and "repelling" mean the same thing.(5 votes)
How do we know if an object will have a negative positive or neutral charge?(3 votes)- The charge of an object can be determined based on the transfer of electrons between objects or the presence of excess or deficit of electrons.
Charging by contact: When two objects come into contact, electrons can be transferred from one object to another. If an object gains electrons, it becomes negatively charged because it now has an excess of negatively charged particles (electrons). If an object loses electrons, it becomes positively charged because it now has a deficit of negatively charged particles.
Charging by friction: When two objects rub against each other, electrons can be transferred between them. The object that has a higher tendency to gain electrons will become negatively charged, while the object that has a higher tendency to lose electrons will become positively charged.
Induction: Induction occurs when a charged object is brought close to another object without direct contact. The presence of the charged object causes a redistribution of charges in the second object. This can result in a separation of charges, leading to one side of the object becoming positively charged and the other side becoming negatively charged.
Conservation of charge: In an isolated system, the total charge remains constant. This means that if electrons are gained by one object, an equal number of electrons are lost by another object, resulting in one object becoming negatively charged and the other positively charged.
It's important to note that the specific charge of an object can depend on various factors, such as the materials involved, the environment, and the presence of other charged objects. The behavior of charges follows the principles of electrical attraction and repulsion, and their distribution can be determined through experimentation and observations.(1 vote)
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.