AFCT Electronics: Components and Functions 3

Question 1

What is the function of a relay in an electronic circuit?

Accepted Answer

To use a small current to control a larger current by electromagnetic switching

Answer

A relay uses an electromagnet energized by a small control current to mechanically open or close a set of contacts, allowing a low-power circuit to control a high-power circuit safely.

Question 2

What does an LED (Light Emitting Diode) require in a circuit to operate safely?

Accepted Answer

A current-limiting resistor in series

Answer

LEDs require a current-limiting resistor in series because they have very low forward resistance once turned on. Without a resistor, excessive current would flow through the LED, quickly destroying it.

Question 3

What is the difference between an NPN and a PNP bipolar junction transistor?

Accepted Answer

NPN conducts when the base is more positive than the emitter; PNP conducts when the base is more negative than the emitter

Answer

In an NPN transistor, current flows from collector to emitter when the base voltage is sufficiently positive relative to the emitter. In a PNP transistor, current flows from emitter to collector when the base is sufficiently negative relative to the emitter.

Question 4

What is the primary purpose of a transformer?

Accepted Answer

To transfer electrical energy between circuits through electromagnetic induction, changing voltage levels

Answer

A transformer uses two or more coils wound around a common magnetic core to transfer AC electrical energy between circuits. It can step up or step down voltage levels while inversely changing current levels.

Question 5

What is the function of an operational amplifier (op-amp) in a circuit?

Accepted Answer

To amplify the voltage difference between its two inputs with very high gain

Answer

An op-amp amplifies the voltage difference between its inverting and non-inverting inputs with extremely high open-loop gain (typically 100,000 or more). With feedback networks, it performs precise amplification, filtering, and mathematical operations.

(AFCT) Armed Forces Classification Test Practice Test

(AFCT) Armed Forces Classification Test Practice Test

AFCT Electronics: Components and Functions 3