Lecture Notes: Electrical Circuits - Vocabulary

Vocabulary flashcards covering key terms from resistor networks, meters, and capacitor circuits described in the lecture notes.

Parallel circuit

A circuit configuration where components are connected across the same two nodes so each component experiences the full battery voltage; adding branches increases total current and reduces the overall resistance.

Series circuit

A circuit configuration where components are connected end-to-end along a single path so the same current flows through all components; the total voltage divides among them.

Equivalent resistance (R_eq) in parallel

The combined resistance of resistors in parallel, given by 1/Req = 1/R1 + 1/R2 + …; Req is smaller than the smallest individual resistor.

Ohm's Law

V = I × R; the fundamental relation between voltage, current, and resistance.

Ammeter

A device that measures current, connected in series; ideal ammeters have zero resistance so they do not affect the circuit.

Voltmeter

A device that measures voltage, connected in parallel; ideal voltmeters have infinite resistance so they draw negligible current and do not affect the circuit.

Ideal ammeter

An ammeter with zero resistance that does not change the current in the circuit.

Ideal voltmeter

A voltmeter with infinite resistance that does not draw current or disturb the circuit.

Total battery current (I_bat)

The total current drawn from the battery, determined by V divided by the total circuit resistance R_eq.

Kirchhoff's Loop Law

The sum of all voltage changes around any closed loop is zero.

Kirchhoff's Junction Law (Current Law)

The sum of currents entering a junction equals the sum leaving; current is conserved.

Series resistance rule

Resistors in series add: R_eq = R1 + R2 + … ; the current is the same through all series components.

Parallel resistance rule

For parallel resistors, 1/Req = 1/R1 + 1/R2 + … (Req is the reciprocal of the sum of reciprocals).

Identifying series vs parallel (caution)

Two resistors may look parallel at one end but are not in parallel if the other ends connect to different nodes.

Circuit reduction strategy

Identify series/parallel groups, replace each group with its equivalent resistance, and repeat until a single R_eq remains.

Current division

In a parallel network, the total current splits among branches; for equal resistors, currents are equal; in general, Ii = V/Ri.

Parallel paths analogy

More lanes on a highway allow more cars to flow without changing the speed limit (voltage) across each path.

Check-as-you-go

Verify intermediate results by applying Kirchhoff’s laws to prevent errors when rebuilding circuits.

Capacitor

A device that stores electrical energy as charge; Q = C × V, and charging continues until V_C equals the source voltage.

Q = C × V

Charge stored on a capacitor equals its capacitance times the voltage across it.

Fully charged capacitor condition

When charging ends, the capacitor voltage V_C equals the source voltage E and current drops to zero.

Capacitors in parallel

In parallel, capacitors have the same voltage across them; total capacitance is Ceq = C1 + C2 + …; total charge Qtotal = Q1 + Q2 + ….

Capacitors in series

Capacitors share the same charge Q; the voltages add: Vtotal = V1 + V2 + …; Ceq = 1/(1/C1 + 1/C2 + …).

C_eq in parallel

Equivalent capacitance when capacitors are in parallel equals the sum: C_eq,parallel = C1 + C2 + ….

C_eq in series

Equivalent capacitance when capacitors are in series is given by 1/Ceq = 1/C1 + 1/C2 + …; the series combination has a smaller Ceq than the individual capacitors.

Charge distribution in parallel capacitors

Total charge stored in parallel capacitors is Q_total = (C1 + C2 + …) × V (same voltage V across all).

Voltage distribution in series capacitors

In series, the same charge flows through each capacitor while voltages add to the total voltage.

Q across parallel capacitors

The total charge on parallel capacitors equals the sum of individual charges: Q_total = Q1 + Q2 + ….

Voltage across parallel capacitors is the same

All capacitors in parallel have the same voltage across them equal to the source voltage.

Circuit analysis steps (reduce, rebuild, analyze)

Reduce the circuit to an equivalent R, compute total current, then rebuild to find individual currents/voltages.

Capacitance unit

Farad (F); common subunits include microfarad (µF) for practical circuits.