Step 1: A silicon diode's forward I–V readings: (0.50 V, 0.2 mA), (0.60 V, 1.5 mA), (0.70 V, 12 mA), (0.75 V, 35 mA). Estimate the cut-in voltage and the dynamic resistance at 12 mA. Step 2: Plot I vs V: current is negligible below ~0.6 V then rises steeply — the knee (cut-in) is at ≈ 0.65–0.70 V, characteristic of silicon. Step 3: Dynamic resistance r_d = ΔV/ΔI around the operating point. Between (0.70 V, 12 mA) and (0.75 V, 35 mA): ΔV = 0.05 V, ΔI = 23 mA. Step 4: r_d = 0.05/0.023 ≈ 2.2 Ω — tiny, showing the diode is fully on. Step 5: Reverse bias check: at −5 V the current is ~2 μA (reverse saturation), a factor of ~10⁴ smaller than forward current. Result: Cut-in ≈ 0.7 V; r_d ≈ 2 Ω when on; reverse current ~μA — the one-way valve behaviour.