This physics problem tests your understanding of fundamental physical laws and their applications. The step-by-step solution below breaks down the problem using relevant equations and physical reasoning.
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You're on a roll — Here are the solutions for the questions from Section III, Option 3: OPTION 3: ELECTRONICS 1. (a) (i) The underlined phrase "a bandset clearly picks the signals from the radio station" refers to the tuning or resonance phenomenon in a radio receiver circuit. A tuning circuit is designed to resonate at a specific frequency, allowing it to select and amplify signals at that frequency while rejecting others. 1. (a) (ii) Assumption: The circuit in Figure 4 is an LC resonant circuit, and the inductor has a value of L = 12 mH (based on typical values for such problems). Step 1: Convert given values to SI units. Inductance L = 12 mH = 12 × 10^-3 H Capacitance C = 2.7 pF = 2.7 × 10^-12 F Step 2: Use the formula for resonant frequency f. f = (1)/(2(LC)) Step 3: Substitute the values and calculate f. f = (1)/(2((12 × 10^-3) H)) × (2.7 × 10^-12 F) f = (1)/(2(32.4 × 10^-15) s)^2 f = (1)/(2(3.24 × 10^-14) s)^2 f = (1)/(2 × 1.8 × 10^-7) s f = (1)/(1.13097 × 10^-6) s f ≈ 884200 Hz f ≈ 884.2 kHz The transmitting frequency is 884 kHz. 1. (b) (i) The underlined phrase "d.c. gain of 100" means that for every unit of direct current (d.c.) flowing into the base of the transistor, 100 units of d.c. will flow through the collector. It is the ratio of the collector current to the base current (_dc = (I_C)/(I_B)). 1. (b) (ii) Step 1: Identify the given values. d.c. gain _dc = 100 Base current I_B = 22.5 A Step 2: Calculate the collector current I_C. I_C = _dc × I_B I_C = 100 × 22.5 A = 2250 A I_C = 2.25 mA Step 3: Calculate the emitter current I_E. The emitter current is the sum of the base and collector currents. I_E = I_B + I_C I_E = 22.5 A + 2250 A = 2272.5 A I_E = 2.2725 mA The collector current is 2.25 mA and the emitter current is 2.27 mA. Send me the next one 📸