A torch bulb glows if the terminals of the bulb are connected to the terminals of a cell by the metallic wire.

Answer

**Step-by-Step Solution:**

1. **Understanding the Components**: A torch bulb consists of a filament, which is a thin wire that glows when electricity passes through it. A cell (or battery) provides the electrical energy needed to light the bulb.

2. **Connecting the Circuit**: When the terminals of the bulb are connected to the terminals of a cell using metallic wires, a closed circuit is formed. This means there is a complete path for the electric current to flow.

3. **Current Flow**: Once the circuit is complete, the electric current flows from the positive terminal of the cell, through the metallic wire, into one terminal of the bulb, through the filament, and back to the negative terminal of the cell via another wire.

4. **Heating the Filament**: As the electric current passes through the filament of the bulb, it encounters resistance. This resistance causes the filament to heat up.

5. **Glowing of the Bulb**: When the filament gets hot enough due to the resistance, it starts to emit light. This is why the bulb glows when connected to the cell.

6. **Conclusion**: Therefore, the bulb glows because the electric current flowing through the filament heats it up, causing it to emit light.

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