AC Circuits

PIRA classification 5L

Grayed Demos are either not available or haven't been built yet


5L10. Impedence


Demonstration Name



inductive choke

Move a core in and out of a coil in series with a light bulb.


variable inductance

An inductor with an movable iron core is connected in series with a light bulb.


inductive reactance

Pull a core in and out of a solenoid in series with a 200W lamp, then a 10 W lamp. Try with DC.


inductor with lamp on AC

Place a large coil in series with a light bulb, then insert an iron core in the coil and the light bulb dims.


capacitive impedence

A variable capacitor is connected in series with a light bulb.


capacitive reactance

A circuit to vary R through the value of the capacitive reactance, among other things.


capacitive reactance

Measure the voltage and phase across each element in a circuit with a 25W lamp in series with a capacitor.


skin effect

Conductors of different dimensions are connected to lamp indicators in a high frequency circuit.


skin effect

Stack metal plates between the primary and secondary of a transformer, a bundle of wire is opened up to gain access to any wire for a current measurement.



Some phasemeter circuits are given suitable for showing current-voltage relationships for reactive elements.


I-V curves on a scope

A circuit to generate I-V curves of various electrical components. Diagram, Appendix: p. 1337.



A simple circuit used by technicians to probe the relationship of current and voltage in a circuit.


impedence bridge

Complex impedances are plugged into a Wheatstone bridge board.

5L20. LRC Circuits - AC


Demonstration Name



LCR - phase differences

Applied voltage, R, L, and C are displayed on a four channel scope while L is changed and the circuit passes through resonance.


parallel resonance

Transformers permit viewing voltages in all elements of a parallel RLC circuit.


phase shift in an LRC circuit

The voltages across elements of a RLC circuit are shown as the inductor is varied through resonance.


LCR series circuit

Isolation transformers permit viewing applied, R, L, and C simultaneously on an oscilloscope as the inductor is varied through resonance.


series RLC phase shift on scope

Simultaneous display of four traces of the RLC circuit on a single channel scope using a multiplexer. Circuit diagrams are given.


RLC phase relationships

A circuit allows phase relationships between R and L or C of the Cenco 80375 choke coil and resonance apparatus to be displayed on an oscilloscope.


LCR waveforms display

The Leybold double wire loop oscillograph is modified to project laser beams showing the current and voltage relationships of a LRC (circuit given) circuit.


LCR phase relationships

Show the input and output of an RLC circuit on a dual trace oscilloscope.


phase shift in fluorescent circuit

Among other things, demonstrate the phase shift in a fluorescent lamp circuit.


LC op amp interface

OP amps placed across the inductor and capacitor have high impedance and do not perturb the system.


LCR - phase differences

A neon lamp detector shining on a disk rotated by a synchronous motor shows phase differences in a series RLC circuit driven by 110 V AC.


LCR vectors on CRO

Pulses are generated from an RLC circuit to modulate the Z axis of a CRO. The dots shift as the applied frequency is changed.


seconds period LCR

Directions for building an underdamped LCR circuit with a period from .5 to 5 seconds. Forced oscillation with a electromechanical generator.


driven LRC circuit

The voltage and current across the capacitor, inductor, resistor, and supply are shown in succession on an oscilloscope.


RLC - resonance

A large lamp lights in a 60 Hz 120 V RLC circuit when the L is changed and resonance is achieved.


series LRC circuit

The light bulb in a RLC circuit glows when the inductor core is moved through resonance.


series RLC resonance

A 110 VAC lamp, capacitor, and variable inductor form a series circuit.


series RLC resonance

Short out the capacitor in a RLC circuit with a light bulb resistance.


parallel AC resonance

A capacitor and variable inductor tuned to resonate in parallel at 60 Hz have series light bulb current indicators.


parallel resonance

A RLC series resonant circuit with a variable inductor and light bulb indicators.


RLC - resonance

A variable inductor and capacitor in series with a lamp driven by 110 V AC. Short inductor or capacitor, vary both.


resonance at 60 Hertz

The product of inductance in henrys and capacitance in microfarads should be 7.


LC parallel resonance

An LC circuit is driven by coupling a second coil driven by an audio oscillator. Reference: AJP 36(1),x.


resonance curves on scope

A crude but effective spectrum analyzer circuit for generating and displaying frequency response curves on an oscilloscope


RLC resonance plot on scope

An x-y plot of the resonance curve is generated by mechanically driving a pot controlling the x axis of the scope by a chain to the tuning knob of the signal generator. Diagram, Picture.


coupled RLC circuits

Two identical RLC circuits and a driving coil are coupled with a common core. The two are shown to resonate at the same frequency, then when both are operated simultaneously, there are two different frequencies at which resonance occurs. Diagram, Picture.


air coupled circuit

Two coils are air coupled, one is driven by an audio oscillator and various capacitors are placed across the other coil while the output is monitored on an oscilloscope.


high voltage RLC ringing

The secondary of a high voltage transformer is shunted across a spark gap, Leyden jars, and an inductor made of several turns of heavy copper all in series.


HF RLC resonance

A 30 MHz 500W generator is coupled to a loop, light bulb, parallel plate RLC circuit and the capacitance changed to find resonance. Picture.

5L30. Filters and Rectifiers


Demonstration Name



bridge rectifier

Plug in diodes on a Wheatstone bridge circuit board are used to demonstrate unrectified, half wave, and full wave rectification. Show on an oscilloscope.


bridge rectifier

Half and full wave rectification with a plug in Wheatstone bridge board.


wheatstone bridge

A Wheatstone bridge board with plug in elements.


rectifier circuit

Diodes in a Wheatstone bridge configuration followed by two low pass filters.


bridge rectifier

A circuit allows switching between unrectified, half, and full wave rectified configurations. A magnet bob pendulum and pickup coil provide a slow ac signal.


diode rectifier

Use neon lamps to indicate rectification with a diode rectifier tube.


thermionic rectifier

Kenotron type thermionic rectifier using a switch to change polarity of dc voltage.


very low frequency rectification

Rectification can be demonstrated with a rotary potential divider and a vacuum tube in one of the standard circuits. Other stuff too.


blinky whirligig

A small flashing light on the end of a string is whirled around.


blinky whirlygig

An improvement on TPT,22(7),448, "AC made visible".


blinky whirligig

Blinking neon bulb on a cord is swung around in uniform circular motion.


blinky whirligig

Swing a light bulb around and take a picture of it with a fan strobed Polaroid


glow lamp swinger

Swing a GE A9A or Chicago Miniature Ne-23 neon glow lamp in a 3 foot radius circle. Use as a persistence of vision demo by holding it still.


whirling glow lamp

A two watt neon glow lamp is mounted on a hand rotator.


AC and DC with starch and iodine

Drawing an electrode across a starch/iodine solution gives a solid line with dc and a dashed line with ac.


LC low pass filter

Ammeters measure the current before and after a LC filter while an audio amplifier detects ac before and after as the frequency is varied.


current in an LC circuit

Lamps are in series in each branch of an LC circuit to show current distribution as inductance is changed.


Fourier zeros LC circuit

No energy is deposited in a resonant high Q circuit at f=n/pulse width. Circuit given.


mechanical analog of LC filter

A string and pulley arrangement provides an analog of a parallel LC filter. Reference: AJP 14(5),318.


RLC filter

A RLC parallel filter with each component individually switched is used to show the effect of each component on audio frequencies.


resonant cavity properties

Identical ultrasonic transducers are bonded to opposite parallel faces of a solid medium. One is pulsed with a rf voltage at the transducer resonant frequency and the other is the receiver. The frequency adjusted to a Fabry-Perot resonance.


many circuits

Nine simple circuits using diodes and transistors covering from rectifiers to a linear sweep generator.