The correct option is (a).
Explanation
A Light Emitting Diode (LED) is a semiconductor device that emits light when an electric current passes through it. It operates on the principle of electroluminescence and functions as a p-n junction diode.
Statement 1 is Correct:
LEDs are highly sensitive to electric current and can glow even with very weak currents. In contrast, traditional incandescent bulbs require a significant amount of current to heat the filament to a temperature where it emits visible light. Therefore, LEDs are preferred in testers to detect weak currents that might not be sufficient to light up a standard bulb.
Statement 2 is Incorrect:
An LED is a type of diode, which allows current to flow in only one direction (forward bias). It has specific polarity: a positive terminal (anode), typically indicated by a longer lead, and a negative terminal (cathode), indicated by a shorter lead. If connected in reverse polarity (reverse bias), the LED acts as an open switch and does not glow.
Statement 3 is Incorrect:
LEDs are known for their high energy efficiency. They consume significantly less electricity than standard incandescent bulbs or fluorescent tubes to produce the same amount of light. Most of the energy in incandescent bulbs is wasted as heat, whereas LEDs convert a higher percentage of electrical energy directly into light.
Key Takeaway:
LEDs are unidirectional optoelectronic devices that require correct polarity to function. They are characterized by low power consumption and the ability to operate on very low currents, making them superior to filament bulbs for testing and indication purposes.