Question

I–V characteristics for a junction diode is shown. The device is

• A. LED
• B. Solar cell
• C. Photo cell
• D. Zener diode

Hint:

Any device whose I–V characteristic lies in the fourth quadrant acts as a power source. Solar cells are classic examples of such devices.

Answer 1

The Correct Option is B

Step 1: Understanding the given I–V characteristic.
The I–V graph shows that current flows even when the voltage is zero or negative. The curve lies in the fourth quadrant, indicating that the device supplies electrical power rather than consuming it. Such a characteristic is typical of a device that converts light energy into electrical energy.
Step 2: Analyzing the options.
(A) LED: An LED conducts mainly in forward bias and emits light. Its I–V characteristic does not show power generation in the fourth quadrant. Hence, this option is incorrect.
(B) Solar cell: A solar cell generates current when illuminated and shows an I–V characteristic in the fourth quadrant. This exactly matches the given graph. Hence, this option is correct.
(C) Photo cell: A photo cell mainly works on the photoelectric effect and does not show the same I–V characteristics as a junction diode solar cell. Hence, this option is incorrect.
(D) Zener diode: A Zener diode operates in reverse breakdown region for voltage regulation and does not generate power. Thus, this option is incorrect.
Step 3: Conclusion.
Since the given I–V characteristic shows power generation and corresponds to a junction device operating in the fourth quadrant, the device is a solar cell.