All Exams Test series for 1 year @ ₹349 only
Question

Which electrical bias is required for an LED to emit light?

The correct answer is

Forward bias

An LED is a p–n junction diode. When it is forward biased, electrons from the n-side and holes from the p-side are pushed into the junction region.

There they recombine, and in a direct band-gap semiconductor (such as GaAs or GaAsP) the energy released in each recombination is emitted as a photon of light — electroluminescence.

Under reverse bias, the depletion region widens and almost no carriers cross the junction, so there is no recombination and no light. At zero bias or in open circuit, no current flows and the LED stays dark.

Hence, the answer is Forward bias.

Was this answer helpful?

Important Questions from Light Emitting Diode (LED)

  1. The color of the emitted light from the P-N junction made of GaAsP is
  2. A light-emmiting diode (LED) converts :

  3. Which of the following statements about LED is INCORRECT?

  4. An LED has a rating of 2 V and 10 mA. If it is connected to a 6V battery, the minimum value of series resistance is

  5. An LED driver circuit does NOT have a/an _________.

Need Expert Advice?
Upcoming Exams
RRB JE
October 27, 2026
RRB ALP
November 03, 2026
Test Series
RRB Technicians img
Railways
RRB Technician Grade 1 (Signal) 2026 Mock Test Series
270 Tests 3 Tests Free
7598 Attempts
4.8(211)
English, Hindi, Bengali +7 More
More Questions from RRB Technicians

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App