Question 1

When the SCR is connected into a DC circuit, the gate can turn the SCR off, but cannot turn it on.

Accepted Answer

In a DC circuit, the gate of an SCR (Silicon Controlled Rectifier) can trigger it to turn on, but once on, the gate loses control and cannot turn it off; turning off an SCR in a DC circuit requires removing the forward bias or reducing the current below its holding level.

Question 2

The current through the anode-cathode circuit of an SCR must drop below the ____ level before the device will turn off.&#10;A) charging current&#10;B) falloff current&#10;C) saturation current&#10;D) holding current

Accepted Answer

The current must drop below the holding current level before an SCR (Silicon Controlled Rectifier) will turn off. The holding current is the minimum current required to keep the SCR in the conducting state. Once the current falls below this level, the SCR switches off.

Question 3

Most devices that operate by ionization have a characteristic known as ____.&#10;A) positive resistance&#10;B) positive conversion&#10;C) negative resistance&#10;D) negative current

Accepted Answer

Most devices that operate by ionization, such as gas discharge tubes and neon lights, exhibit a characteristic known as negative resistance. This means that as the voltage increases, the current through the device actually decreases, which is opposite to the behavior of devices with positive resistance, where current increases with voltage.

Question 4

By ____ of a gate circuit, the gate current reaches 5 ma sooner.&#10;A) increasing the resistance&#10;B) increasing the current&#10;C) reducing the resistance&#10;D) reducing the current

Accepted Answer

Reducing the resistance in a gate circuit allows the gate current to reach its target value faster because less resistance means a higher current can flow through the circuit more readily.

Question 5

A(n) ____ is a gas-filled tube and depends on ionization of the gas for operation.&#10;A) neon lamp&#10;B) fluorescent lamp&#10;C) incandescent lamp&#10;D) LED lamp

Accepted Answer

Neon lamps are gas-filled tubes that rely on the ionization of gas (usually neon) to produce light.

Question 6

The gate turns the SCR on, but the AC waveform dropping ____ will turn it off.&#10;A) back to -1 volts&#10;B) back to 0 volts&#10;C) below 0 volts&#10;D) below 5 volts

Accepted Answer

The answer of The gate turns the SCR on, but...

Question 7

The SCR only controls half of the positive cycle of alternating current applied to it.

Accepted Answer

The SCR is a unidirectional device, which means that it only allows current to flow in one direction. In the case of alternating current, the SCR only allows current to flow during the positive half of the cycle.

Question 8

When connecting an SCR in an AC circuit, the first thing to remember is that the SCR is not a rectifier.

Accepted Answer

SCR (Silicon Controlled Rectifier) is indeed a type of rectifier used in AC circuits to control power. It allows current to flow only when a gate signal is applied, effectively rectifying AC to DC.

Question 9

The only difference between an SCR and a common rectifier diode is that the SCR can be triggered to turn on at a specific point in the waveform.

Accepted Answer

An SCR (Silicon Controlled Rectifier) can be triggered to conduct at a specific point in the waveform, unlike a common rectifier diode which conducts whenever forward-biased.

Question 10

The SCR can be controlled as to when it turns on.

Accepted Answer

The Silicon Controlled Rectifier (SCR) can be controlled by the gate signal; its turn-on time is determined by the moment the gate receives an appropriate triggering signal.

Deck 18: The Scr in an Ac Circuit