PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A circuit contains an ideal 20 V battery, a double-pole switch S that can connect the left-hand portion of the circuit to either position 1 or position 2, a 5.0 Ω resistor R₁, a 15 Ω resistor R₂, a 10 Ω resistor R₃, a 10 Ω resistor R₄, and a 200 μF capacitor C.
• When S is in position 1, the battery, R₁, R₂, and the capacitor are connected in series in that order; R₃ and R₄ are disconnected.
• After the capacitor has been connected in position 1 for a long time, the switch is moved instantaneously to position 2. In position 2, the battery is completely disconnected, and the charged capacitor is now connected to a closed loop that contains only R₃ and R₄ in series.
Assume ideal components and zero resistance in the switch and connecting wires.
(a) While the switch is in position 1 and the circuit has reached steady state, calculate the potential difference across the capacitor.
(b) Immediately after the switch is moved to position 2, determine the magnitude and direction of the current through R₃.
(c) Immediately after the switch is moved to position 2, determine the potential difference across R₄.
(d) Describe qualitatively how the current through R₃ will evolve from the moment the switch is moved until the circuit again reaches steady state. Justify your answer.