Which device is an electric lamp consisting of a wire filament that emits light when heated and is non-ohmic?

Which device is an electric lamp consisting of a wire filament that emits light when heated and is non-ohmic?

• A. Filament bulb
• B. Thermistor
• C. LDR
• D. Diode

Answer: (A)

The main idea is a light source that emits light because its wire filament is heated to a high temperature. A filament bulb does this with a tungsten filament so hot that it glows and emits visible light. As current flows, the filament heats up, and its resistance changes with temperature—specifically, it increases as it gets hotter. That change means the current is not simply proportional to voltage, so the device is non-ohmic. Other options don’t fit the description of a heated-wire lamp. A thermistor and a light-dependent resistor have resistances that vary with temperature or light, but they don’t emit light themselves. A diode conducts mainly in one direction and has a forward voltage drop, but it’s not a heated-filament lamp either.

The main idea is a light source that emits light because its wire filament is heated to a high temperature. A filament bulb does this with a tungsten filament so hot that it glows and emits visible light. As current flows, the filament heats up, and its resistance changes with temperature—specifically, it increases as it gets hotter. That change means the current is not simply proportional to voltage, so the device is non-ohmic.

Other options don’t fit the description of a heated-wire lamp. A thermistor and a light-dependent resistor have resistances that vary with temperature or light, but they don’t emit light themselves. A diode conducts mainly in one direction and has a forward voltage drop, but it’s not a heated-filament lamp either.