Explain the working principles of metallic and mercury thermometers.

Here's how metallic and mercury thermometers work:

• Metallic Thermometer: These often use a bimetallic strip, which consists of two different metals bonded together. When heated, the metals expand at different rates, causing the strip to bend or coil. This mechanical movement is then used to move a pointer across a calibrated scale, indicating the temperature.

• Mercury Thermometer: This type relies on the thermal expansion of mercury. A small bulb containing mercury is connected to a narrow capillary tube. When the thermometer is exposed to heat, the mercury expands and rises up the capillary tube. The height of the mercury column directly corresponds to the temperature, which is read against a scale etched on the glass.