 Solution

ID: past-exam-of-the-physics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2016/paper-1/section-c/c10/b/solution

The capacitor stores electrostatic energy, the inductor stores magnetic energy, and the resistor converts energy into heat. Their instantaneous values are

E_{C} = \frac{q ^{2}}{2 C} = \frac{1}{2} C V_{C}^{2}, E_{I} = \frac{1}{2} L I^{2}, P_{R} = R I^{2} .

The sign convention for electric current does not change these expressions. With the initial voltage,

E_{C} (0) = C V_{0}^{2} /2 = 90 μ J

and

E_{I} (0) = P_{R} (0) = 0

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