Electronic Devices Quiz - ICSE Class 12 Physics
Free practice quiz: Electronic Devices (ICSE Class 12 Physics). 46 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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A p-n junction diode is forward biased. If the applied voltage is increased from $V_1$ to $V_2$ where $V_2 > V_1$, what happens to the barrier potential and the diffusion current?
- Barrier potential decreases, diffusion current increases
- Barrier potential increases, diffusion current decreases
- Barrier potential decreases, diffusion current decreases
- Barrier potential increases, diffusion current increases
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Answer: A. Barrier potential decreases, diffusion current increases
In forward bias, the applied voltage opposes the internal barrier potential of the p-n junction. As the applied voltage increases, it effectively reduces the barrier potential, allowing more majority carriers to diffuse across the junction. This increased diffusion leads to a higher diffusion current. The drift current, due to minority carriers, remains relatively constant.
What is the primary function of a filter circuit in a DC power supply following a rectifier?
- To increase the output voltage
- To reduce the ripple in the DC output
- To convert DC to AC
- To regulate the input AC voltage
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Answer: B. To reduce the ripple in the DC output
Rectifiers produce pulsating DC. Filter circuits, typically using capacitors and sometimes inductors, smooth out these pulsations (ripples) to provide a more steady and constant DC output voltage, making it suitable for powering electronic devices.
A Light Emitting Diode (LED) is essentially a forward-biased p-n junction that emits light due to:
- Blackbody radiation
- Bremsstrahlung effect
- Electroluminescence
- Photoelectric effect
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Answer: C. Electroluminescence
Electroluminescence is the phenomenon where a material emits light in response to an electric current or field. In an LED, when the p-n junction is forward-biased, electrons and holes recombine in the depletion region, releasing energy in the form of photons (light). The color of the emitted light depends on the semiconductor material used.
A tunnel diode exhibits negative differential resistance due to:
- Thermal runaway
- Avalanche breakdown
- Quantum mechanical tunneling
- High doping concentration
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Answer: C. Quantum mechanical tunneling
The negative differential resistance (NDR) characteristic of a tunnel diode arises from the quantum mechanical tunneling of electrons across a very narrow depletion region. As the forward voltage increases, the probability of tunneling initially increases, leading to a current rise, but then decreases as the energy levels for tunneling become misaligned.
Which semiconductor device is most suitable for use as a high-speed switch due to its extremely short switching time?
- Bipolar Junction Transistor (BJT)
- PN Junction Diode
- MOSFET
- SCR (Silicon Controlled Rectifier)
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Answer: C. MOSFET
MOSFETs are generally considered to have faster switching times than BJTs, especially at very high frequencies. This is primarily because MOSFET switching is controlled by the movement of majority carriers and does not suffer from minority carrier storage effects, which slow down BJTs. SCRs are designed for power switching and are generally slower.