From the activity 1, we have seen that there are two types of charges. Let us discuss some other properties of electric charge.
a) Unlike charges attract and like charges repel.
b) Charge is conserved
In activity 1, we have discussed that balloon acquires negative charges when rubbed with wool. From where are these charges generated? Is any new charge created? Does this charge creation obey any conservation law?
We have already discussed ( in activity 1), the fact that when bodies are charged by rubbing, there is transfer of electrons from one body to the other; Charges are neither created nor destroyed.
The negative charge acquired by balloon is exactly equal to the charge lost by wool. If we take balloon and wool as a system, we can summaries the above mentioned facts as total charge on an isolated system* remains constant. This is called conservation of charge.
Sometimes, nature creates charged particles: a neutron turns into a proton and an electron. The proton and electron thus created have equal and opposite charges and the total charge is zero before and after the creation.
Another example is found in the fission reaction. Charge before and after fission is the same
c) Electric Charge is Quantized:
We have discussed the transfer of charges during rubbing. What is the minimum quantity of charge transferred from one material to another material?
Any physical quantity is said to be quantized if it can take only discrete values. Energy of an electron in a particular orbit and wavelength of a stationary wave produced on a stretched string are examples. Each electron/ proton carries a charge of magnitude 1.6*10^-19 C. This is the elementary or basic amount of charge. We cannot find stable charges which are fractions of these. Charge on any body is the integral multiple of electronic charge. This is called quantization of charge.
ie, q= +or- ne where n = 1,2,3,..
We can have bodies with charge +5e, -16e, but not 3.62e. Any amount of charge in the universe can be expressed as an integral multiple of the basic amount of charge e.
The quantization of charge was first suggested by the experimental laws of electrolysis discovered by the English experimentalist Faraday. It was experimentally demonstrated by Millikan in 1912.
(d) Additivity of Charges
What will happen if two equally and oppositely charged bodies (balloon and wool) are brought in contact?
If a system contains two point charges q1 and q2, the total charge of the system is obtained simply by adding algebraically q1 and 12, If a system contains n charges q1,q2,q3,....qn, then the total charge of the system is q1+q2+q3+.......+qn. Proper signs have to be used while adding the charges of a system containing five group of charges +7, +2,-8,+4 and -6, in some arbitrary unit, is(+7) +(+2)+(-8)+(-6)=-1 in the same unit.
NOTE
If the size of charged bodies are very small compared to distance between them, we treat them as a point charge. All the charge content of the body is assumed to be concentrated at one point in space.
a) Unlike charges attract and like charges repel.
b) Charge is conserved
In activity 1, we have discussed that balloon acquires negative charges when rubbed with wool. From where are these charges generated? Is any new charge created? Does this charge creation obey any conservation law?
We have already discussed ( in activity 1), the fact that when bodies are charged by rubbing, there is transfer of electrons from one body to the other; Charges are neither created nor destroyed.
The negative charge acquired by balloon is exactly equal to the charge lost by wool. If we take balloon and wool as a system, we can summaries the above mentioned facts as total charge on an isolated system* remains constant. This is called conservation of charge.
Sometimes, nature creates charged particles: a neutron turns into a proton and an electron. The proton and electron thus created have equal and opposite charges and the total charge is zero before and after the creation.
Another example is found in the fission reaction. Charge before and after fission is the same
c) Electric Charge is Quantized:
We have discussed the transfer of charges during rubbing. What is the minimum quantity of charge transferred from one material to another material?
Any physical quantity is said to be quantized if it can take only discrete values. Energy of an electron in a particular orbit and wavelength of a stationary wave produced on a stretched string are examples. Each electron/ proton carries a charge of magnitude 1.6*10^-19 C. This is the elementary or basic amount of charge. We cannot find stable charges which are fractions of these. Charge on any body is the integral multiple of electronic charge. This is called quantization of charge.
ie, q= +or- ne where n = 1,2,3,..
We can have bodies with charge +5e, -16e, but not 3.62e. Any amount of charge in the universe can be expressed as an integral multiple of the basic amount of charge e.
The quantization of charge was first suggested by the experimental laws of electrolysis discovered by the English experimentalist Faraday. It was experimentally demonstrated by Millikan in 1912.
(d) Additivity of Charges
What will happen if two equally and oppositely charged bodies (balloon and wool) are brought in contact?
If a system contains two point charges q1 and q2, the total charge of the system is obtained simply by adding algebraically q1 and 12, If a system contains n charges q1,q2,q3,....qn, then the total charge of the system is q1+q2+q3+.......+qn. Proper signs have to be used while adding the charges of a system containing five group of charges +7, +2,-8,+4 and -6, in some arbitrary unit, is(+7) +(+2)+(-8)+(-6)=-1 in the same unit.
NOTE
If the size of charged bodies are very small compared to distance between them, we treat them as a point charge. All the charge content of the body is assumed to be concentrated at one point in space.
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