Principles of Electronics 578: Power Control using Semiconductor Devices

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What is the primary purpose of a diac in a triac-based circuit?

To provide a stable reference voltage for the triac

To act as a voltage regulator for the triac

To trigger the triac into conduction (correct)

To protect the triac from reverse biasing

Which of the following is NOT a common application of a diac?

Light dimming

Heat control

Universal motor speed control

Voltage regulation (correct)

In a diac-triac based lamp dimmer circuit, what is the purpose of the series $R_4$-$C_1$ circuit across the triac?

To limit the rate of voltage rise across the triac during switch off (correct)

To filter out noise in the input voltage

To provide a stable reference voltage for the diac

To adjust the phase of the voltage across the triac

What is the purpose of using a diac to trigger a triac in a circuit?

To provide a more reliable and faster turn-on of the triac Signup and view all the answers

What is the relationship between the breakover voltage and holding current of a diac?

The breakover voltage and holding current values are identical for the forward and reverse regions of operation Signup and view all the answers

Which of the following is a key advantage of using a diac to trigger a triac in a circuit?

More reliable and faster turn-on of the triac Signup and view all the answers

What is the key characteristic of an SCR that allows it to control the flow of AC power?

It can only conduct current in one direction Signup and view all the answers

How can the phase angle of the gate voltage in an SCR circuit be adjusted?

By adjusting the variable resistance R1 Signup and view all the answers

What is the primary advantage of using a triac to control AC power, compared to an SCR?

Triacs can control both positive and negative half-cycles of AC Signup and view all the answers

Which of the following is NOT a common application of a triac?

DC motor speed control Signup and view all the answers

In the triac circuit shown in Fig. 21.11, what happens when the switch S is thrown to position 1?

The triac is cut off and the lamp is off Signup and view all the answers

What is the primary reason triacs are often used as electronic on/off switches controlled by mechanical switches?

Triacs require low gate currents and voltages Signup and view all the answers

What is the primary advantage of using semiconductor switching devices over electrical methods for controlling power flow?

They provide finer control over power flow. Signup and view all the answers

Which of the following semiconductor switching devices can control alternating current in a load?

Triac Signup and view all the answers

What is the primary limitation of a silicon controlled rectifier (SCR) that necessitates the use of a triac?

Both A and B Signup and view all the answers

Which of the following semiconductor switching devices is used for controlled rectification, inversion, and regulation of power in a load?

All of the above Signup and view all the answers

What is the primary purpose of using semiconductor switching devices in power control applications?

All of the above Signup and view all the answers

Which of the following statements is true about triacs?

Triacs are three-terminal semiconductor switching devices. Signup and view all the answers

Principles of Electronics 578: Power Control using Semiconductor Devices

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