36) A thyristor can be fired with dv/dt of 100 V/µs. If the forward breakover current of the device is 5 mA. The value of diffusion capacitance is given by : (1) 25 pF (2) 2.5 pF (3) 50 pF (4) 5.0 pF Answer: Option C i = C*dV/dt or, 5 * 10^(-3) = C * 100/10^(-6) or, C = 5 * 10^(-3) / 100 * 10^(-6)          = 0.05 * 10^(9)         = 50 pF Previous yr Question papers with Full Explanations → UGC-NET : Electronics Science Study Materials →

Understanding the Basic Concept The difficulty here is that the numerical solution jumps directly to formulas without explaining what a buck converter and the inductor are doing physically. Step 1: What is a Step-Down (Buck) Converter? A buck converter takes a higher DC voltage and produces a lower DC voltage by rapidly turning a switch ON and OFF . Input voltage = 230 V Desired average output voltage = 50 V Since the switch is not ON all the time, the load sees an average voltage lower than 230 V. The fraction of time the switch is ON is called the duty cycle (D) . V o = D × V s Here: D = 50 / 230 = 0.217 This means the switch is ON only about 21.7% of the time and OFF for 78.3% of the time. Step 2: Why Do We Need an Inductor? Imagine connecting the load directly to the switching voltage: 230 V → ON 0 V → OFF 230 V → ON 0 V → OFF The current would jump up and down violently. An inductor resists sudden chang...

35) An R-L load is connected to a 230V, 400 Hz step down dc converter. The average load current is 100 A. The load resistance is 0.5 Ohm. The allowed ripple limit is 15%. The minimum value of inductor to limit the maximum ripple current is : (1) 66.7 mH (2) 6.67 mH (3) 1.67 mH (4) 16.7 mH Answer: Option B Solution This is a standard single-phase step-down (buck) chopper design problem. Given Supply voltage, Vs = 230 V Chopper frequency, f = 400 Hz Average load current, Io = 100 A Load resistance, R = 0.5 Ω Ripple current limit = 15% First find the average output voltage: Vo = Io × R = 100 × 0.5 = 50 V For a buck converter, Vo = DVs So the duty ratio is D = 50 / 230 = 0.2174 Ripple Current Allowed peak-to-peak ripple current: ΔI = 0.15 × 100 = 15 A For a buck converter operating in continuous conduction mode (CCM), ΔI =...

  Can Someone See Your JWT Access Token in the Browser? Is Your Authentication Secure? During technical interviews and application security reviews, developers are often asked: "I can see your JWT access token in the browser. Is your application secure?" This question tests your understanding of authentication security, token storage, browser behavior, and protection against common attacks such as Cross-Site Scripting (XSS). Can Someone See a JWT Access Token in the Browser? Yes. In many web applications, JWT access tokens are visible within browser developer tools. This visibility alone does not automatically indicate a security vulnerability. Common places where JWT tokens may appear include: Browser Local Storage Session Storage ...

  Why Does CORS Error Occur Between Localhost:3000 and Localhost:8000? Complete Guide & Solutions If your frontend application is running on http://localhost:3000 and your backend API is running on http://localhost:8000 , you may encounter a CORS (Cross-Origin Resource Sharing) error. Many developers assume that because both services run on localhost, they belong to the same origin. However, browsers treat them as different origins due to their different port numbers. What Is an Origin in Web Development? An origin consists of three components: Protocol (HTTP or HTTPS) Host (localhost, example.com, etc.) Port (3000, 8000, 8080, etc.) For example: http://localhost:3000 http://localhost:8000 Although both ...

Condition K = 0 (No Direct Path) Rayleigh PDF p(r) = (r/σ 2 ) e -r 2 /2σ 2 Doppler Spectrum S(f) ∝ [1 - (f/f m ) 2 ] -0.5 Urban Parameters Max Doppler (Speed) 30 Hz Path Loss (Shadowing) 1.0 ⚠️ DEEP FADE DETECTED! Simulation: Rayleigh Fading represents 100% multipath. Note that the signal frequently drops to near-zero (Deep Fades), which is the primary challenge in mobile communications. FREQUENCY DOMAIN: Classic Jakes "Bowl" Spectrum TIME DOMAIN: Rayleigh Envelope (Note De...

Linear K-Factor Ratio K = P_los / P_diffuse LoS Doppler Shift f_d = f_max · cos(θ) Rician Envelope PDF p(r) = (r / σ 2 ) e -(r 2 + ν 2 ) / 2σ 2 I 0 (rν / σ 2 ) Parameters K-Factor (dB) 6 dB Max Doppler (Hz) 30 Hz Angle of Arrival (θ) 45° Simulation Logic: We use the Jakes Sum-of-Sinusoids model with 8 oscillators to generate the Rayleigh component, then vector-add the Dominant Path based on the Angle θ. Model: Jakes Sum-of-Sinusoids (8 oscillators) + LoS Component. ...

34) In optical Communication system the Zero-dispersion wave length is given by : (1) 0 nm (2) 1310 nm (3) 1550 nm (4) 800 nm Answer: Option B Previous yr Question papers with Full Explanations → UGC-NET : Electronics Science Study Materials →