Physic Labs

Problem 2

A capacitor C charged to V₀ discharges through resistor R, with q(0)=CV₀. Find q(t) and discharge current i(t). Use the stated ideal model: quantities are constant or vary only as specified, with no extra drag, losses, or external influences. State a sign convention, keep units consistent, and use a classical approximation only where appropriate. (a) Set up the governing equation from a fundamental law. (b) Solve for the requested quantity under the stated conditions. (c) Check the result using a suitable limit, sign, or unit test, and report both the expression and its physical meaning.
dq/dt=−q/(RC)dq/dt=-q/(RC)
problems.proof.analysis

Solve the relation for the unknown while preserving algebraic signs and physical restrictions. Use any stated geometry or definition to express the result in the given data.

problems.proof.pitfall. Since i_out leaves the initially positive plate, i_out=-dq/dt; the minus sign reflects its decreasing charge.