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#static charge

2 public questions tagged with this topic.

Applications of EM Waves in Communication and Medicine

What type of charges cannot produce electromagnetic waves?

**Microwaves in ovens** cause water molecules to rotate at 2.45 GHz, friction heats food, penetration depth few cm, efficient heating, also radar uses reflection of microwaves from objects, Doppler shift measures speed, medical diathermy uses microwaves for tissue heating. The document states that neither stationary charges nor charges in uniform motion (steady currents) can produce electromagnetic waves; only accelerated charges can. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Stationary charges, illustrating EM wave transverse nature and Maxwell's displacement current concept.

Ref: NCERT > Physics Book > Electromagnetic Waves > Applications of EM Waves in Communication and Medicine

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Electric Charge, Quantization and Conservation

A plastic rod gains a charge of \( -1.92 \times 10^{-7} \, \text{C} \) when rubbed. How many electrons were transferred

**Charge conservation and quantization** govern rubbing processes where electrons transfer without creation. Total charge before and after remains equal, and any measured charge corresponds to n = q/e electrons, allowing counting of carriers from coulomb value. Negative charge means electrons gained. q = n e , e = -1.6 × 10⁻¹⁹ C . n = (q/|e|) = (1.92 × 10⁻⁷/1.6 × 10⁻¹⁹) = 1.2 × 10¹² . Substituting values gives 1.2 × 10¹², which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.

Ref: NCERT > Physics Book > Electric Charges and Fields > Electric Charge, Quantization and Conservation

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