The two charges repel each other. If a positive charge and a negative charge interact, their forces act in the same direction, from the positive to the negative charge.
As a result opposite charges attract each other:. The electric field and resulting forces produced by two electrical charges of opposite polarity. Lekner thinks that with modern techniques, it should be relatively straightforward to test his theory experimentally.
But there are several hurdles. Grier points out that the attraction will be weakened in an ordinary metal where the electrical resistance would hinder the redistribution of electrical charge, though it might work better in superconductors. Ducker thinks it could be easier at small scales, because the spheres would have to be smooth enough to feel the attraction before they touched.
Also, one would have to be able to control the charge on each sphere, and to suppress uncontrolled charge transfer between them. All the same, Ducker may have a go. Lekner, J. Download references. You can also search for this author in PubMed Google Scholar. Swirling dust shocks physicists Apr What toys can tell us Oct Why opposites don't always attract Sep John Lekner. Electric forces are repulsive for objects of like charge and attractive between objects of the opposite type of charge or between charged objects and neutral objects.
On two occasions, the following charge interactions between balloons A, B and C are observed. In each case, it is known that balloon B is charged negatively. Based on these observations, what can you conclusively confirm about the charge on balloon A and C for each situation. However, A would also attract B if it were neutral. If C repels B, then you know for certain that it has the same type of charge as C - that is, a - charge.
Upon entering the room, you observe two balloons suspended from the ceiling. You notice that instead of hanging straight down vertically, the balloons seems to be repelling each other. You can conclusively say Observing a repulsive interaction is sufficient evidence to conclude that both balloons are charged.
However, further testing or additional information would be required to determine the type of charge the balloons have.
Jean knows that object A is negatively charged and object B is electrically neutral. It's best to start on the right side of the table. Since D and E attract, D must have the opposite charge of E. If C has like charge as D, it must be - also. Two objects are charged as shown at the right. Having the same type of charge, they will repel. Two objects are shown at the right.
One is neutral and the other is negative. Balloons X , Y and Z are suspended from strings as shown at the right. Negatively charged balloon X attracts balloon Y and balloon Y attracts balloon Z. List all that apply. Y is observed to attract a negatively charged object balloon X.
So Y could be either positively charged or neutral. Y attracts Z. So A and B are two possible answers. But Y could be positively charged. And if Y were positively charged, the Y-Z attraction would be observed if Z were neutral. So choice C is also possible. Physics Tutorial. My Cart Subscription Selection. So you see gravity is universally attractive! So ultimately this sign comes from the fact that photons carry one unit of spin and the fact that the interactions between photons and matter particles have to obey the rules of special relativity.
Notice the remarkable interplay of relativity and quantum mechanics at work. When put together these two principles are much more constraining than either of them individually! Indeed it's quite remarkable that they get along together at all. A poetic way to say it is the world is a delicate dance between these two partners. Now why do atoms and molecules generally attract? This is actually a more complicated question! The force between atoms is the residual electrical force left over after the electrons and protons have nearly cancelled each other out.
Here's how to think of it: the electrons in one atom are attracted to the nuclei of both atoms and at the same time repelled by the other electrons. So if the other electrons get pushed away a little bit there will be a slight imbalance of charge in the atom and after all the details are worked out this results in a net attractive force, called a dispersion force. There are various different kinds of dispersion forces London, van der Waals, etc. But they are all basically due to residual electrostatic interactions.
Further reading: I recommend Matt Strassler's pedagogical articles about particle physics and field theory. He does a great job at explaining things in an honest way with no or very little mathematics. The argument I went through above is covered in some capacity in just about every textbook on quantum field theory, but a particularly clear exposition along these lines with the math included is in Zee's Quantum Field Theory in a Nutshell.
This is where I would recommend starting if you want to honestly learn this stuff, maths and all, but this is an advanced physics textbook despite being written in a wonderful, very accessible style so you need probably at least two years of an undergraduate physics major and a concerted effort to make headway in it.
Because careful physicists have made an innumerable number of observations and have found that this is what nature does. There is a long history of observations before any theory could be solidified. Classical electromagnetic theory modeled the behavior of charges very well , with Maxwell's equations. They show how, when positive and negative charges exist in nature they can be modelled with accurate mathematical solutions of the equations and one could think that your "why" would be answered by " because they fulfill Maxwell's equations".
Then quantum mechanics came as a revolutionary mathematical theory to describe phenomena measured in the microcosm, including charged elementary particles, and a theory was developed as explained in Michael Brown's answer above, which again models extremely well the behavior of charged particles, and your "why" can be answered by "because they fulfill quantum electrodynamical equations".
You must perceive then that the "why opposite charges attract" with the answer "because that is what we have observed" becomes "because we have modeled mathematically the observations successfully".
Then the question becomes why this mathematical model, and the answer is "because it describes the observations", circular.
I am pointing out that "why" questions can not be answered with physics. Physics can be successfully modeled mathematically with postulates and using the model one can show how the behavior of positive and negative charges under all sorts of experimental conditions can be predicted accurately, but not "why" they exist. The why gets the answer "because that is what we have observed nature to do". Well the mutual repulsion of like particles, such as electrons for example is commonly explained as being due to "exchange particles" that mediate the four standard forces of the standard model.
For the Electro-magnetic force Coulomb between like charges electrons the exchange particle is the Photon. Two electrons in the vicinity of each other "exchange" a photon with each other back and forth that results in the mutual repulsion. Imagine two ice skaters facing each other on smooth ice.
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