1. **Problem Statement:** Write the Kirchhoff's Voltage Law (KVL) equation for the circuit shown in Figure 1.1. 2. **KVL Principle:** The sum of all voltages around any closed loop in a circuit is zero. 3. **Identify Voltages and Directions:** Starting at the lower left corner and moving clockwise, the voltages are: - Voltage source $v_a$ (negative when moving from positive to negative terminal), - Voltage drop across resistor $R_1$ is $v_1 = iR_1$, - Voltage source $v_b$, - Voltage drops across resistors $R_2$ and $R_3$ are $v_2 = iR_2$ and $v_3 = iR_3$ respectively. 4. **Write the KVL equation:** $$-v_a + v_1 + v_b + v_2 + v_3 = 0$$ 5. **Substitute voltage drops with Ohm's law:** $$-v_a + iR_1 + v_b + iR_2 + iR_3 = 0$$ 6. **Group terms:** $$v_b - v_a = i(R_1 + R_2 + R_3)$$ This equation relates the voltage sources and the current through the resistors in the loop.