Daily review: Transformers | Photodiode | LED…

Q: What is the primary function of the core in a transformer?

To provide a low reluctance path for magnetic flux — The core is designed to maximize magnetic coupling between windings by providing a low reluctance path for the flux.

Q: Which operating mode is a photodiode typically used in for high-speed applications?

Reverse bias mode — Reverse bias reduces the junction capacitance, significantly increasing the response speed of the photodiode.

Q: In an LED, light is emitted due to which process?

Recombination of electrons and holes — LEDs emit light when electrons in the conduction band recombine with holes in the valence band, releasing energy as photons.

Q: What happens to the output voltage of a transformer if the load current increases, assuming an ideal transformer?

It remains constant — An ideal transformer maintains a constant output voltage ratio based on the turns ratio, independent of the load.

Q: Why is the bandgap energy of the semiconductor material critical in an LED?

It determines the wavelength (color) of the emitted light — The energy of the emitted photon equals the bandgap energy, which directly dictates the wavelength and color of the light.

Q: What is the purpose of the 'dark current' in a photodiode?

It is the small leakage current that flows in the absence of light — Dark current is the small reverse leakage current that persists in a photodiode even when no incident light is present.

Q: In a step-down transformer, if the turns ratio (Np/Ns) is 10:1, what happens to the output current compared to the input current?

It is 10 times larger — In an ideal transformer, power (V*I) is constant. A 10:1 voltage step-down results in a 1:10 current step-up.

Q: Which material is NOT commonly used in the construction of visible light LEDs?

Silicon (Si) — Silicon has an indirect bandgap, making it extremely inefficient at emitting light compared to direct bandgap materials like GaN or GaAs.

Q: Transformer cores are laminated to reduce which type of losses?

Eddy current losses — Lamination breaks up the path for circulating currents, effectively reducing eddy current losses within the core.

Q: What is the primary difference between a photodiode and a solar cell?

A solar cell is meant to generate power, while a photodiode is meant to detect signals — While both convert light to electricity, solar cells are optimized for power harvesting, whereas photodiodes are optimized for speed and sensitivity.

Question 1 of 10

What is the primary function of the core in a transformer?

The core is designed to maximize magnetic coupling between windings by providing a low reluctance path for the flux.

Question 2 of 10

Which operating mode is a photodiode typically used in for high-speed applications?

Reverse bias reduces the junction capacitance, significantly increasing the response speed of the photodiode.

Question 3 of 10

In an LED, light is emitted due to which process?

LEDs emit light when electrons in the conduction band recombine with holes in the valence band, releasing energy as photons.

Question 4 of 10

What happens to the output voltage of a transformer if the load current increases, assuming an ideal transformer?

An ideal transformer maintains a constant output voltage ratio based on the turns ratio, independent of the load.

Question 5 of 10

Why is the bandgap energy of the semiconductor material critical in an LED?

The energy of the emitted photon equals the bandgap energy, which directly dictates the wavelength and color of the light.

Question 6 of 10

What is the purpose of the 'dark current' in a photodiode?

Dark current is the small reverse leakage current that persists in a photodiode even when no incident light is present.

Question 7 of 10

In a step-down transformer, if the turns ratio (Np/Ns) is 10:1, what happens to the output current compared to the input current?

In an ideal transformer, power (V*I) is constant. A 10:1 voltage step-down results in a 1:10 current step-up.

Question 8 of 10

Which material is NOT commonly used in the construction of visible light LEDs?

Silicon has an indirect bandgap, making it extremely inefficient at emitting light compared to direct bandgap materials like GaN or GaAs.

Question 9 of 10

Transformer cores are laminated to reduce which type of losses?

Lamination breaks up the path for circulating currents, effectively reducing eddy current losses within the core.

Question 10 of 10

What is the primary difference between a photodiode and a solar cell?

While both convert light to electricity, solar cells are optimized for power harvesting, whereas photodiodes are optimized for speed and sensitivity.

Daily review: Transformers | Photodiode | LED (Light Emitting Diode) Quiz