Electric heaters and incandescent bulbs use Joule heating (H = $I^{2}$Rt). Nichrome is used in heaters (high resistivity + high melting point). Tungsten filament bulbs glow because of intense Joule heating at operating temperature (~2500°C).

Fuses and circuit breakers protect electrical circuits. A fuse wire has a low melting point; when current exceeds the rated value, the $I^{2}$R heating melts it, breaking the circuit. Fuse rating is the maximum safe current.

Resistance thermometers (RTDs) use R = $R_{0}$(1 + α$\Delta T$) to measure temperature with high precision. Platinum RTDs (PT-100) are industry standards because platinum has a very stable and nearly linear α (~$3.85 \times 10^{-3}$/°C) over a wide range.

NTC thermistors are semiconductor temperature sensors where resistance decreases with temperature (α < 0). Used in digital thermometers, fever strips, engine temperature monitoring, and battery management systems.

Strain gauges use the Wheatstone bridge configuration. A conducting element bonded to a surface changes its resistance when stretched (because l changes and A changes). The bridge circuit detects tiny resistance changes, converting mechanical strain to an electrical signal. Used in load cells, force sensors, and structural health monitoring.

Potentiometers in everyday devices: The volume knob on a radio, the fuel level gauge in a car, the throttle position sensor in an engine — all use the potentiometer principle of variable voltage division along a resistive element.

Battery internal resistance measurement: A battery's state of health can be assessed by measuring its internal resistance via potentiometer. A fresh battery has very low r; as it ages, r increases, causing terminal voltage to drop significantly under load (dim headlights, slow engine cranking).

Household wiring (parallel circuits): All household appliances are connected in parallel so that each device receives the full supply voltage (220 V in India), operates independently, and can be switched on or off without affecting others. A single fault in one branch does not disable the entire circuit.

Electroplating and electrolysis use controlled current from cells with known EMF and internal resistance to deposit materials with precise thickness. The formula H = $I^{2}$Rt determines heat generated in the electrolytic cell.

Digital multimeters measure both DC and AC voltages, currents, and resistances. The resistance measurement mode applies a known small current and measures the resulting voltage (V = IR), automatically displaying R. High-accuracy measurements use 4-wire (Kelvin) sensing to eliminate lead resistance.