DC Circuits Topic

Ohm's Law

Concept 2 demos

Ohm's Law

A light bulb, ammeter, and voltmeter are connected in a circuit controlled by a Variac. Gradually increasing the voltage and comparing and at each step reveals the relationship -- and …

Optima car battery with red top connected by yellow cables to a wooden board holding a knife switch with thin iron wire mounted across the terminals

Resistance and Current

Shows that electrical hazard depends on current, not voltage alone. Touching a 12V car battery with your hand is safe (~1 MΩ body resistance, ~12 μA), but shorting the same …

Power and Energy

Concept 3 demos

GE watthour meter mounted on a black display board with a 40W incandescent bulb on the left, control switch box in front, and a 13W compact fluorescent bulb on the right

Power Meter

A household-style watthour meter measures real-time power consumption of various loads. Students observe the disc spin rate change with different devices and learn the relationship between power and energy .

Four globe-style incandescent bulbs labeled 100W, 60W, 60W, and 40W in ceramic sockets on clear acrylic bases, wired in series and powered on; brightness increases from left to right with the 40W bulb glowing brightest

Power in Series

Four incandescent bulbs of different wattage ratings are wired in series. Students predict which will be brightest, then discover the 40W bulb outshines the 100W bulb — because in a …

Four glass-tube fuses with metal end caps; one has an intact coiled filament, three show darkened glass and broken filaments from blowing

Fuses

Compare intact and blown glass fuses under a document camera or overhead projector to show how excessive current causes heating that melts the fuse filament. The darkened glass in blown …

Circuit Analysis

Concept 7 demos

Honeywell portable potentiometer in a wooden case, showing rotary dials, decade selector knobs, and a center-zero galvanometer on the front panel

Commercial Potentiometer

Students examine commercial potentiometers to see how null-balance techniques enable precise voltage measurement without drawing current from the source. These instruments make voltage division and null detection tangible in a …

Demonstration potentiometer on lecture bench with slide wire along a ruler scale, center galvanometer, resistance box, standard cell, 6V battery, and projection meter displayed on the wall above

Demonstration Potentiometer

Students observe the potentiometer method for measuring unknown voltages by null-balance comparison against a standard cell. A projected galvanometer shows the class how precision voltage measurement works without drawing current …

Demonstration Wheatstone bridge on a clear acrylic frame with horizontal slide wire along a centimeter ruler, center-zero galvanometer mounted above, two plug-in resistor positions at top, and an Energizer 6V battery connected below

Slide-Wire Wheatstone Bridge

Students observe how a Wheatstone bridge measures unknown resistance by adjusting a slide wire until the galvanometer nulls. Swapping plug-in resistors of different values shows how bridge sensitivity degrades when …

RC Circuits

Concept 4 demos

Two incandescent bulbs on clear plastic bases with white ceramic sockets connected by wires to a large blue Nichicon 50V capacitor; the left bulb near the capacitor is dim while the right bulb is brightly lit

Capacitor and Light Bulbs

Students observe capacitor charging and discharging through the brightness of incandescent bulbs. One bulb fades as the capacitor charges (decreasing current), then both bulbs glow equally during discharge, making exponential …

Wooden-framed RC demonstrator board with transparent acrylic panel, large horizontal electrolytic capacitor, small incandescent bulb at top, and knife switch at bottom right, connected to a Xantrex DC power supply reading 9.0V

RC Demonstrator

Demonstrates RC circuit transient behavior through a visible flashing bulb. Students observe that an uncharged capacitor initially passes current (bulb flashes) but blocks DC once fully charged, connecting exponential charge/discharge …

RC circuit with power supply reading 2.88V (left), large electrolytic capacitor in test tube clamp, SPDT switch, incandescent bulb on dark base, and two multimeters labeled I and V both reading zero

Current and Voltage in RC Circuit

Shows RC charging and discharging in real time. Students observe exponential decay of current and voltage on multimeters while an incandescent bulb provides a visual indicator that dims as the …

Instruments

Concept 4 demos

Leeds & Northrup galvanometer in black case mounted on cast iron tripod stand with leveling screws, mirror and suspended coil visible through front window, terminal block on top

L & N Galvanometer

Students learn how a galvanometer detects small currents through the deflection of a suspended coil in a magnetic field. A mirror on the suspension reflects a laser beam onto a …

Welch demonstration galvanometer with center-zero scale (5-0-5), black metal housing with visible coil mechanism, circuit diagrams for VOLTS and AMPS configurations on the dial face, red binding posts and knobs on base

Demonstration Galvanometer

Shows how the same galvanometer movement becomes either a voltmeter (with a series multiplier resistor) or an ammeter (with a parallel shunt resistor). Students see that these are not fundamentally …

RCA Dynamic Demonstrator: four color-coded boards (blue AC Volts, red DC Volts, green DC Current, orange Ohms) with exposed circuit components and an RCA analog multimeter mounted at top center

Demonstration Multimeter

Students see the internal circuitry normally hidden inside analog multimeters. The demonstration boards show how series multiplier resistors, parallel shunt resistors, and bridge rectifiers adapt a single galvanometer movement to …