Question 1

A device that can be implemented to phase shift an SCR is the four-layer diode or ____ diode.&#10;A) SUS&#10;B) Shockley&#10;C) Shockley Unilateral Switch&#10;D) SRS

Accepted Answer

The correct term for a four-layer diode that can be implemented to phase shift an SCR (Silicon Controlled Rectifier) is the Shockley diode.

Question 2

The Shockley diode will remain turned off until its ____ voltage is reached.&#10;A) breakover&#10;B) saturation&#10;C) falloff&#10;D) limit

Accepted Answer

The Shockley diode remains turned off until its breakover voltage is reached, at which point it switches to the conducting state.

Question 3

The pulses produced by the UJT are dependent upon the AC voltage connected to the anode of the SCR.

Accepted Answer

The pulses produced by a Unijunction Transistor (UJT) are not dependent on the AC voltage connected to the anode of a Silicon Controlled Rectifier (SCR); they are primarily determined by the UJT's intrinsic properties and the external circuit configuration.

Question 4

An SCR must be phase shifted to gain complete control of the AC waveform supplied to it.

Accepted Answer

Phase shifting an SCR allows control over the point in the AC waveform at which the SCR begins conducting, thus controlling the output power.

Question 5

The silicon unilateral switch is fundamentally different than the Shockley diode.

Accepted Answer

Both the Silicon Unilateral Switch (SUS) and the Shockley diode are four-layer (PNPN) semiconductor devices and operate on similar principles, with the main difference being in their specific applications and electrical characteristics, rather than their fundamental operation.

Question 6

The breakover voltage can be adjusted to a value that is less than the original value if no zener diode were to be used, but it cannot be adjusted to a higher value.

Accepted Answer

The breakover voltage is the voltage at which a zener diode starts to conduct. If no zener diode is used, the breakover voltage is the voltage at which the transistor starts to conduct. This voltage can be adjusted to a lower value by using a resistor in series with the transistor, but it cannot be adjusted to a higher value.

Question 7

The Shockley diode has a ____ characteristic very similar to the UJT.&#10;A) negative current&#10;B) positive current&#10;C) negative resistance&#10;D) positive resistance

Accepted Answer

The Shockley diode exhibits a negative resistance characteristic similar to the Unijunction Transistor (UJT), which means its resistance decreases as the voltage across it increases, after reaching a certain threshold.

Question 8

The unijunction transistor (UJT) was developed to do the job of phase shifting SCR circuits.

Accepted Answer

The UJT was developed to replace phase-shifting SCR circuits, which were complex and expensive.

Question 9

The charge time for a(n) ____ is determined by its capacitance and the resistance of resistor one.&#10;A) transformer&#10;B) inverter&#10;C) transistor&#10;D) capacitor

Accepted Answer

The charge time for a capacitor is determined by its capacitance and the resistance it is connected to, often described by the time constant τ = RC, where R is the resistance and C is the capacitance.

Question 10

The operating characteristic of the UJT is that of a ____.&#10;A) pulse timer&#10;B) pulse inverter&#10;C) pulse transformer&#10;D) pulse rectifier

Accepted Answer

The operating characteristic of the UJT (Unijunction Transistor) is that of a pulse timer. It is commonly used in timing circuits, triggering circuits for thyristors, and as a pulse generator due to its unique ability to produce very sharp pulses.

Deck 20: Ujt Phase Shifting for an Scr