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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Here's the solution to your circuit problem: 11.2.1 To calculate the ammeter reading when switch S is closed, we first find the total resistance of the circuit. Step 1: Calculate the equivalent resistance of resistors P and R, which are connected in parallel. R_PR = (R_P × R_R)/(R_P + R_R) R_PR = (10 \, × 15 \, )/(10 \, + 15 \, ) R_PR = (150 \, ^2)/(25 \, ) = 6 \, Step 2: Calculate the total external resistance (R_ext). Resistor Q is in series with the parallel combination of P and R. R_ext = R_PR + R_Q R_ext = 6 \, + 10 \, = 16 \, Step 3: Calculate the total resistance of the circuit (R_total), including the internal resistance (r). R_total = R_ext + r R_total = 16 \, + 2 \, = 18 \, Step 4: Calculate the total current (I_total) using Ohm's law for the entire circuit. This is the ammeter reading. I_total = ER_total I_total = 6 \, V18 \, = (1)/(3) \, A The ammeter reading is 0.33 A. 11.2.2 The switch S is now open. Step 1: When switch S is opened, resistor R (15 ) is removed from the circuit. The external circuit now consists only of resistor P (10 ) in series with resistor Q (10 ). The new total external resistance (R'_ext) is: R'_ext = R_P + R_Q = 10 \, + 10 \, = 20 \, The new total resistance of the circuit (R'_total) is: R'_total = R'_ext + r = 20 \, + 2 \, = 22 \, Step 2: Compare the new total resistance (22 \, ) with the previous total resistance (18 \, ). The total resistance has increased. Step 3: According to Ohm's law (I = ER_total), if the total resistance increases while the EMF remains constant, the total current will decrease. The new total current (I'_total) would be: I'_total = 6 \, V22 \, = (3)/(11) \, A ≈ 0.27 \, A Since 0.27 \, A < 0.33 \, A, the ammeter reading will DECREASE. Step 4: Reason: When switch S is opened, resistor R is removed from the parallel branch. This increases the total external resistance of the circuit. According to Ohm's law, an increase in total resistance leads to a decrease in the total current flowing through the circuit. The ammeter reading will DECREASE. 11.2.3 The voltmeter measures the terminal potential difference (V_terminal = E - Ir). From 11.2.2, we determined that when switch S is opened, the total current (I) in the circuit decreases. Since the EMF (E) and internal resistance (r) are constant, a decrease in I means that the voltage drop across the internal resistance (Ir) will decrease. Therefore, V_terminal = E - Ir will increase because a smaller value is subtracted from the constant EMF. The voltmeter reading will INCREASE. 11.2.4 The voltmeter measures the terminal potential difference, which is given by the formula V_terminal = E - Ir. When switch S is opened, the total external resistance of the circuit increases, causing the total current (I) to decrease. Since the internal resistance (r) is constant, a decrease in the total current (I) results in a smaller voltage drop (Ir) across the internal resistance. Consequently, the terminal potential difference (V_terminal) increases because a smaller amount is subtracted from the constant EMF (E). Send me the next one 📸