Class 12th Physics-Electric Charges and Fields- Fundamental Concepts of electric Charge -part-2
Class 12th Physics-Electric Charges and Fields- Fundamental Concepts of electric Charge -part-2
Sure! Here’s a Class 12 Physics explanation of the chapter “Electric Charges and Fields”, focusing on:
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Chapter: Electric Charges and Fields
Topic: Fundamental Concepts of Electric Charge – Part 2
Class: 12th CBSE/NCERT
Quick Recap from Part 1:
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Electric charge is a basic property of matter.
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It can be positive (like proton) or negative (like electron).
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Like charges repel, unlike charges attract.
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Charge is quantized and conserved.
Part 2: Fundamental Concepts Continued
1. Quantization of Charge
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Charge exists in discrete packets, not continuous.
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Smallest unit of charge = charge of an electron
e=1.6×10−19 Coulombse = 1.6 \times 10^{-19} \, \text{Coulombs}
Formula:
Any charge q=±n⋅eq = \pm n \cdot e
Where:
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nn = any integer (1, 2, 3, …)
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ee = elementary charge
Example:
If a body has charge q=3.2×10−19 Cq = 3.2 \times 10^{-19} \, C, then:
n=q/e=2n = q/e = 2 → It has 2 extra electrons
2. Conservation of Charge
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Charge can neither be created nor destroyed, only transferred.
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Total charge before and after any physical process remains constant.
Example:
In rubbing a glass rod with silk:
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Glass loses electrons → becomes positively charged
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Silk gains electrons → becomes negatively charged
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Net charge = 0 (balanced)
3. Additivity of Charge
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Charges are scalars (they add algebraically).
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Total charge = Sum of individual charges
Example:
If a body has +3 C and -2 C on different parts,
Net charge = 3C−2C=+1C3C – 2C = +1C
4. Methods of Charging
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Friction:
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By rubbing two objects (e.g., balloon on hair)
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Transfers electrons
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Conduction (Contact):
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Charged object touches a neutral object
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Charge gets shared
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Induction:
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No contact needed
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A charged object brought near induces opposite charge in a conductor
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Real-Life Application:
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Electrostatic dust precipitators use electric charge to clean factory smoke.
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Photocopiers and laser printers work using charge principles.
Summary (Key Points):
| Concept | Key Idea |
|---|---|
| Quantization | Charge = n × e |
| Conservation | Total charge remains same |
| Additivity | Charges add up algebraically |
| Methods of Charging | Friction, Conduction, Induction |
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