| s,p,d,f subshell notation | Angular Momentum Quantum Number |
| S-100 | Short-distance busses |
| S-R latch | The S-R latch |
| sample frequency | Nykquist Frequency |
| Sample frequency, ADC | Practical considerations of ADC circuits |
| saturable reactor | Special transformers and applications |
| Saturation | Permeability and saturation |
| Saturation voltage | Negative feedback |
| | Transistor Ratings |
| Saturation, transistor | The transistor as a switch |
| | Active mode operation |
| Sawtooth wave | More on spectrum analysis |
| | AC Waveforms |
| Scalar number | Introduction |
| | Power in resistive and reactive AC circuits |
| Scale, logarithmic | Ohmmeter design |
| Schmitt trigger | Logic signal voltage levels |
| | Schmitt Trigger |
| Schottky diode | Schottky diodes |
| scientific mode | Hand calculator use |
| Scientific notation | Scientific notation |
| SCR | Other waveshapes |
| | Ionization (gas-filled) tubes |
| | The Silicon-Controlled Rectifier (SCR) |
| SCR bridge rectifier | The Silicon-Controlled Rectifier (SCR) |
| Screen | The tetrode |
| SCS | The Silicon-Controlled Switch (SCS) |
| SCSI | Short-distance busses |
| Seal-in contact | Motor control circuits |
| | Programmable logic controllers |
| secondary cell | Electron activity in chemical reactions |
| secondary coil | Mutual inductance and basic operation |
| Secondary emission | The tetrode |
| secondary transformer coil | What is alternating current (AC)? |
| Seebeck effect | Thermocouples |
| | Thermoelectricity |
| selectivity | Resonant filters |
| selector switch | Switch types |
| self-inductance | Mutual inductance and basic operation |
| Self-induction | Electromagnetic induction |
| Self-modifying program | Microprocessors |
| Selsyn | AC Instrumentation Transducers |
| | Selsyn (synchro) motors |
| semiconductor | Conventional versus electron flow |
| | Introduction |
| | Introduction |
| | Intrinsic Semiconductor |
| | Current flow in a Semiconductor |
| semiconductor diode | Conventional versus electron flow |
| semiconductor fuse | Fuses |
| semiconductor material | Semiconductor Material |
| Semiconductor, defined | Band Theory of Solids |
| sensitive gate | The Silicon-Controlled Rectifier (SCR) |
| Sensitivity, ohms per volt | Voltmeter impact on measured circuit |
| Sequence, harmonic | Harmonic phase sequences |
| Sequence, phase | Phase rotation |
| Sequences | Algebra Reference |
| sequential access memory | Digital memory terms and concepts |
| sequential logic | Introduction to Shift Registers |
| | Combinational Logic |
| Serial data | Introduction |
| | Shift Register, Parallel-in, Serial-out |
| Series | Series batteries |
| | Rheostat range limiting |
| Series analysis | Series R, L, and C |
| Series batteries | Series batteries |
| Series circuit rules | Simple series circuits |
| | What is a series-parallel circuit? |
| | Series R, L, and C |
| Series circuits | Series and parallel component equivalent values |
| series LC resonance | Simple series resonance |
| Series, definition of | What are "series" and "parallel" circuits? |
| Series-parallel | Parallel batteries |
| Series-parallel analysis | Analysis technique |
| | Series-parallel R, L, and C |
| | Summary |
| series-parallel resonance | Resonance in series-parallel circuits |
| servo motor | Other specialized motors |
| Set state | NOR gate S-R latch |
| Set, latch | The S-R latch |
| Setpoint | Single-ended and differential amplifiers |
| sets | Venn Diagram and Sets |
| setup time, shift register | Shift Register, Serial-in/Serial-out |
| seven-layer model | Network protocols |
| shape symbols, logic gate | Shift Register, Parallel-in, Serial-out |
| shell, electron | Introduction |
| | Quantum physics |
| | Pauli exclusion principle |
| | Quantum Mechanics |
| Shield grounding | Introduction |
| Shielded cable | Introduction |
| shielding | Sensing AC magnetic fields |
| | Sensing AC electric fields |
| shift register | Introduction to Shift Registers |
| | Parallel-In, Parallel-Out, Universal Shift Register |
| | PIPO Universal Devices |
| shift register, parallel-in/serial-out | Shift Register, Parallel-in, Serial-out |
| shift register, serial-in/parallel-out | Serial-in, parallel-out shift register |
| shift register, serial-in/serial-out | Shift Register, Serial-in/Serial-out |
| SHM | An electric pendulum |
| shock | Physiological effects of electricity |
| shock hazard | Physiological effects of electricity |
| | Shock current path |
| | Ohmmeter Usage |
| Shockley diode | The Shockley Diode |
| Short circuit | Resistance |
| | Component failure analysis |
| | A Very Simple Circuit |
| Shunt | Ammeter design |
| shunt resistor | AC Voltmeters and Ammeters |
| | Voltage Follower |
| si systeme | Magnetic units of measurement |
| Siemens | Conductance |
| | Voltage-to-current signal conversion |
| | Active-mode operation |
| Siemens, unit | Susceptance and Admittance |
| Sign-magnitude | Negative binary numbers |
| signal | Analog Signals |
| signal coupling | Introduction |
| | Signal coupling |
| Signal generator | Musical keyboard as a signal generator |
| Signal, 10-50 milliamp | Current signal systems |
| | Voltage-to-current signal conversion |
| Signal, 4-20 milliamp | Current signal systems |
| | Voltage-to-current signal conversion |
| Signal, current | Current signal systems |
| Signal, voltage | Voltage signal systems |
| Significant digit | Scientific notation |
| Silicon-controlled rectifier | Other waveshapes |
| | Ionization (gas-filled) tubes |
| | The Silicon-Controlled Rectifier (SCR) |
| silicon-controlled switch | The Silicon-Controlled Switch (SCS) |
| simple circuit | A Very Simple Circuit |
| Simple combination lock | Simple combination lock |
| Simple Harmonic Motion | An electric pendulum |
| simple op-amp | Simple Op-Amp |
| Simulation, computer | Computer simulation of electric circuits |
| | Voltage divider |
| Simultaneous equations | What is network analysis? |
| Sine wave | AC Waveforms |
| Sines, law of | Trigonometry Reference |
| single electron transistor | Single Electron Transistor |
| Single mode fiber | Optical data communication |
| single phase induction motor | Single-phase induction motors |
| Single-ended amplifier | Single-ended and differential amplifiers |
| Single-phase | Single-phase power systems |
| Single-phasing, electric motor operation | Contactors |
| Sink, current | Current mirrors |
| | CMOS gate circuitry |
| sinusoidal | AC Waveforms |
| Skin effect | Standing waves and resonance |
| | Waveguides |
| | Special transformers and applications |
| | Resonance in series-parallel circuits |
| | Inductor quirks |
| | More on the "skin effect" |
| slicer circuit | Clipper circuits |
| Slide rule | Algebra Reference |
| | Arithmetic with scientific notation |
| slidewire | Potentiometer |
| slip ring, alternator | Automotive alternator |
| Slope (integrating) ADC | Slope (integrating) ADC |
| slow-blow fuse | Fuses |
| Small-scale integration | Operational amplifier models |
| SMD | Resistors |
| Snubber | Inductor commutating circuits |
| Software vs. Hardware | Look-up tables |
| solar cell | Solar Cell |
| soldering | Resistors |
| | Building simple resistor circuits |
| | Transformer -- power supply |
| Solderless breadboard | Building simple resistor circuits |
| | Building series-parallel resistor circuits |
| Solenoid | Relay construction |
| SOP | Larger 4-variable Karnaugh maps |
| SOP expression | Converting truth tables into Boolean expressions |
| Sound cancellation | Sound cancellation |
| sound waves | AC Waveforms |
| Sourc | The NOT gate |
| Source, current | Norton's Theorem |
| | Current signal systems |
| | CMOS gate circuitry |
| Span calibration | Rheostat range limiting |
| Spark gap | Ionization (gas-filled) tubes |
| SPDT switch | Contact "normal" state and make/break sequence |
| Specific resistance | Conductor and Insulator Tables |
| | Specific resistance |
| Spectrum analyzer | Square wave signals |
| | Power quality measurement |
| Spectrum, frequency | Power quality measurement |
| speed switch | Switch types |
| Speedomax | Thermocouples |
| SPICE | Using the Spice Circuit Simulation Program |
| | Computer simulation of electric circuits |
| | Scientific notation in SPICE |
| | Some examples with AC circuits |
| | Voltage divider |
| SPICE netlist | Computer simulation of electric circuits |
| | Scientific notation in SPICE |
| | Simple series circuits |
| SPICE programming | Using the Spice Circuit Simulation Program |
| Spice simulator | Infineon HiPAC-EDT |
| SPICE2g6 | Using the Spice Circuit Simulation Program |
| spin quantum number | Spin Quantum Number |
| spintronics | Spintronics |
| Split phase | Full-wave bridge rectifier |
| Split power supply | Single-ended and differential amplifiers |
| Split-phase | Single-phase power systems |
| SPST switch | Contact "normal" state and make/break sequence |
| | Special-output gates |
| Square wave | Square wave signals |
| | AC Waveforms |
| SR flip-flop | Edge-triggered latches: Flip-Flops |
| SSI | Operational amplifier models |
| Standing wave ratio | Standing waves and resonance |
| Standing waves | Standing waves and resonance |
| Star configuration | Three-phase power systems |
| | Three-Phase Y and Delta Configurations |
| Star topology | Network topology |
| static electricity | Static electricity |
| | Conductors, insulators, and electron flow |
| Static electricity sensor | Static electricity sensor |
| Static RAM | Modern nonmechanical memory |
| stator winding, alternator | Automotive alternator |
| STD | Short-distance busses |
| Steering diode | The NOT gate |
| | TTL NAND and AND gates |
| Step recovery, ADC | Practical considerations of ADC circuits |
| stepper motor | Reluctance motor |
| | Stepper motors |
| stepper motor driver, 3-phase | Ring Counters |
| | Johnson Counters |
| stepper motor driver, unipolar | Ring Counters |
| | Johnson Counters |
| Stored-program computer | Microprocessors |
| Strain gauge | Strain gauges |
| Strip, terminal | Building simple resistor circuits |
| | A Very Simple Circuit |
| Strobing | Asynchronous counters |
| strong nuclear force | Static electricity |
| subscript | Resistors |
| subshell | Quantum physics |
| | Pauli exclusion principle |
| | Quantum Mechanics |
| subtraction | Subtraction |
| Successive approximation ADC | Successive approximation ADC |
| Sum, algebraic | Kirchhoff's Voltage Law (KVL) |
| Sum-Of-Products | Larger 4-variable Karnaugh maps |
| Sum-Of-Products expression | Converting truth tables into Boolean expressions |
| Superconductivity | Conductor and Insulator Tables |
| | Conductors, insulators, and electron flow |
| superconductor | Superconductivity |
| superfluidity | Superconductivity |
| Superposition Theorem | Superposition Theorem |
| | Three-phase power systems |
| | Circuit effects |
| Suppressor | The pentode |
| surface-mount device | Resistors |
| Surge impedance | Finite-length transmission lines |
| susceptance | Susceptance and Admittance |
| SWG (British Standard Wire Gauge) | Conductor size |
| Switch | Resistance |
| | Switch types |
| | Circuit with a Switch |
| Switch contact | Switch contact design |
| Switch contact bounce | Monostable multivibrators |
| Switch debouncing | LED sequencer |
| switch in circuit | Circuit with a Switch |
| Switch normal position | Contact "normal" state and make/break sequence |
| Switch, closed | Resistance |
| Switch, generic contact symbol | Contact "normal" state and make/break sequence |
| Switch, mercury tilt | Switch contact design |
| Switch, open | Resistance |
| Switch, permissive | Permissive and interlock circuits |
| Switch, safety disconnect | Safe practices |
| Switch, tap | Winding configurations |
| switch-tail ring counter | Ring Counters |
| | Johnson Counters |
| Switched digital network | Network topology |
| switched reluctance motor | Reluctance motor |
| switching time | Diode ratings |
| SWR | Standing waves and resonance |
| Synchro | AC Instrumentation Transducers |
| synchronous condenser | Synchronous Condenser |
| Synchronous counter | Synchronous counters |
| synchronous load, shift register | Shift Register, Parallel-in, Serial-out |
| synchronous motor | Synchronous Motors |
| systeme international | Magnetic units of measurement |
| Systems of equations | What is network analysis? |
