All Flashcards
What is the difference between the behavior of capacitors in series vs. parallel?
Series: Same charge on each capacitor; equivalent capacitance is smaller than the smallest individual capacitance. Parallel: Same voltage across each capacitor; equivalent capacitance is the sum of individual capacitances.
Compare the current in an RC circuit at t=0 and t= during charging.
t=0: Current is at its maximum (limited only by the resistance). t=: Current is zero (capacitor is fully charged and blocks current flow).
Compare the voltage across a capacitor at t=0 and t= during charging.
t=0: Voltage across the capacitor is zero (initially uncharged). t=: Voltage across the capacitor is equal to the voltage of the source (fully charged).
Compare capacitor behavior to resistor behavior.
Capacitor: Stores energy in an electric field; opposes changes in voltage. Resistor: Dissipates energy as heat; opposes current flow.
Compare charging and discharging in an RC circuit.
Charging: Capacitor accumulates charge, voltage increases, current decreases. Discharging: Capacitor loses charge, voltage decreases, current decreases.
Define equivalent capacitance.
The single capacitance that has the same effect as a combination of capacitors in a circuit.
Define time constant () in an RC circuit.
The time required for a charging capacitor to reach approximately 63% of its maximum charge or for a discharging capacitor to drop to about 37% of its initial charge. It is given by
Define capacitance.
The ability of a component or circuit to collect and store energy in the form of an electrical charge.
Define resistance.
A measure of the opposition to current flow in an electrical circuit. Resistance is measured in ohms ().
Define electromotive force ().
The voltage generated by a battery or other power source.
How do you calculate the equivalent capacitance of capacitors in series?
Calculate the reciprocal of each capacitance, sum the reciprocals, and then take the reciprocal of the sum: .
How do you calculate the equivalent capacitance of capacitors in parallel?
Sum the individual capacitances: .
Describe the process of a capacitor charging in an RC circuit.
Initially, the uncharged capacitor allows easy charge flow, acting like a wire. As it charges, the charge on the plates increases, the current decreases, and the stored electric potential energy increases, approaching steady-state asymptotically.
Describe the process of a capacitor discharging in an RC circuit.
Charge and stored energy decrease, and current decreases over time. After a time much greater than , the circuit reaches a steady state.
What is the first step to solving a complex RC circuit problem?
Simplify the circuit by finding equivalent capacitances for series and parallel combinations.