Engineering — Circuit Analysis

Capacitance

The ability of a system to store charge per unit voltage, measured in Farads (F).

Inductance

The property of a conductor by which a change in current creates an electromotive force (EMF) in the conductor and nearby conductors, measured in Henrys (H).

What is the time constant in an RC circuit?

The time constant $\tau$ is $RC$, the product of resistance $R$ and capacitance $C$, representing the time it takes to charge the capacitor to ~63.2% of the supply voltage.

Resistor Color Code for 4-band Resistors

First two bands are digits, the third is a multiplier, and the fourth is tolerance. Example: Red-Red-Black-Gold = 22Ω ±5%.

Node Voltage Analysis

A method for determining the voltage at each node relative to a reference node by applying KCL.

Mesh Current Analysis

A method for determining currents in a planar circuit by applying KVL around each mesh.

Superposition Theorem

In a linear circuit with multiple sources, the current or voltage for any element is the algebraic sum of the currents or voltages produced by each source acting independently.

What is the phase relationship between voltage and current in a purely resistive AC circuit?

Voltage and current are in phase, meaning their waveforms peak at the same time.

Impedance

The combination of resistance and reactance in an AC circuit, measured in Ohms (Ω).

RMS Voltage

The root mean square voltage of an AC circuit, equivalent to a DC voltage that delivers the same power.

What is the characteristic impedance of a transmission line?

It is the impedance that a transmission line presents to a signal, determined by the line's inductance and capacitance per unit length.

What is the power factor in AC circuits?

The ratio of real power to apparent power, indicating the efficiency of power usage. It is the cosine of the phase angle $\phi$ between current and voltage.

Maximum Power Transfer Theorem

Maximum power is transferred to the load when the load resistance equals the Thevenin or Norton resistance of the network supplying the power.

What is a Bode Plot?

A graph that represents the frequency response of a system, showing magnitude and phase shift as functions of frequency.

Bandpass Filter

A circuit that allows signals within a certain frequency range to pass while attenuating frequencies outside that range.

Operational Amplifier (Op-Amp)

A high-gain voltage amplifier with differential inputs and typically a single-ended output, used in signal conditioning, filtering, or mathematical operations.

What is slew rate in an op-amp?

The maximum rate of change of output voltage per unit time, typically expressed in volts per microsecond (V/μs).

Zener Diode

A semiconductor device that allows current to flow in the forward direction like a regular diode, but also in the reverse direction if the voltage is larger than the breakdown voltage.

What is a frequency response?

The quantitative measure of the output spectrum of a system or device in response to a stimulus, showing how the system amplifies or attenuates different frequencies.

Total Harmonic Distortion (THD)

A measurement of the harmonic distortion present in a signal, defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency.

What is a voltage divider?

A simple linear circuit that produces an output voltage that is a fraction of its input voltage, typically using two resistors.

What is mutual inductance?

The phenomenon where a change in current in one inductor induces a voltage in another nearby inductor, measured in Henrys (H).

What is a transient response?

The response of a circuit to a change from equilibrium, such as when a switch is turned on or off, before reaching a steady state.