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#electromagnetics

2 public questions tagged with this topic.

AC Through Resistor - Phasor and Power

Why does an ideal transformer maintain constant power across its primary and secondary coils?

**AC through resistor** voltage and current in phase, φ=0°, I = V/R instantaneously, I(t)=I_peak sin ωt, V(t)=V_peak sin ωt, phasor diagram V and I same direction, power instantaneous P = V I = V_peak I_peak sin² ωt, average P_avg = V_rms I_rms = V_rms²/R, always positive, energy dissipated as heat. In an ideal transformer, there are no losses (e.g., resistance, flux leakage). Energy conservation dictates that input power ( V_p I_p ) equals output power ( V_s I_s ), so the power remains constant despite changes in voltage and current. Applying X_L = ωL, X_C = 1/ωC, Z = √(R² + (X_L - X_C)²), I_

Ref: NCERT > Physics Book > Alternating Currents > AC Through Resistor - Phasor and Power

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Applications of EM Waves in Communication and Medicine

What is the typical wavelength range of radio waves used in television communication?

**X-rays and gamma rays in medicine** X-rays imaging because bone absorbs more than tissue, contrast, CT scan uses multiple X-ray projections, gamma knife uses focused gamma rays to destroy tumor with minimal surrounding damage, illustrating high-energy EM wave medical use. The document mentions that TV waves range from 54 MHz to 890 MHz . Using λ = (c/v) , this corresponds to wavelengths from about 0.34 m to 5.56 m . A simpler range based on frequency is used here. Using c = fλ, E₀/B₀ = c, I_d = ε₀ dΦ_E/dt, and spectrum classification λ = c/f, evaluation yields Corresponding to 54 MHz to 890

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

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