Electronics Flashcards

A transformer has a primary winding of 500 turns and a secondary winding of 100 turns. If the primary voltage is 120V, what is the secondary voltage?

Answer: 24V

The turns ratio (500:100 = 5:1) means the secondary voltage is 120V ÷ 5 = 24V.

Which type of capacitor is polarized and must be connected with correct polarity in a circuit?

Answer: Electrolytic

Electrolytic capacitors are polarized due to their construction and will be damaged if connected in reverse polarity.

What is the function of a diode in an AC circuit when used as a half-wave rectifier?

Answer: Allows current to flow in only one direction

A diode passes current in only one direction, so it blocks the negative half-cycle of AC, producing pulsating DC.

In a series RLC circuit at resonance, which statement is TRUE?

Answer: Impedance is at minimum and equals R

At resonance, XL equals XC and they cancel, leaving only resistance R as the total impedance.

What does a multimeter measure when set to the 'ohms' setting?

Answer: Resistance

The ohms setting measures electrical resistance; the meter applies a small voltage and measures the resulting current to calculate resistance.

Which component is commonly used to regulate voltage in a power supply by maintaining a constant output voltage despite load changes?

Answer: Zener diode

A zener diode is designed to operate in reverse breakdown at a specific voltage, making it ideal for voltage regulation.

A circuit draws 3 amps from a 12V battery. What is the power consumed?

Answer: 36 watts

Power (P) = Voltage (V) × Current (I) = 12V × 3A = 36 watts.

What is the purpose of a bypass capacitor placed across a power supply pin on an integrated circuit?

Answer: To filter out high-frequency noise on the supply line

Bypass capacitors provide a low-impedance path to ground for high-frequency noise, keeping the supply voltage clean and stable.

In a transistor amplifier circuit, what region of operation is the transistor in when it acts as a switch in the 'ON' state?

Answer: Saturation

In saturation, both junctions are forward-biased and the transistor conducts maximally, acting like a closed switch.

What is the unit of inductance?

Answer: Henry

Inductance is measured in henries (H), named after Joseph Henry who discovered electromagnetic induction independently.

Two resistors of 6Ω and 3Ω are connected in parallel. What is the equivalent resistance?

Answer: 2Ω

For parallel resistors: 1/R = 1/6 + 1/3 = 1/6 + 2/6 = 3/6, so R = 2Ω.

Which type of logic gate produces a HIGH output only when ALL inputs are HIGH?

Answer: AND gate

An AND gate output is HIGH (1) only when every input is HIGH (1); any LOW input forces the output LOW.

What happens to the capacitive reactance (XC) of a capacitor as frequency increases?

Answer: It decreases

XC = 1/(2πfC), so as frequency (f) increases, XC decreases — capacitors pass high-frequency signals more easily.

What is the primary purpose of a heat sink attached to a transistor or voltage regulator?

Answer: To dissipate heat and prevent thermal damage

Heat sinks increase surface area to transfer heat away from the component into the surrounding air, preventing overheating.

Which semiconductor device can be used to amplify a signal using three terminals: gate, source, and drain?

Answer: MOSFET

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) uses gate, source, and drain terminals and controls current via an electric field.

In a full-wave bridge rectifier, how many diodes are required?

Answer: 4

A bridge rectifier uses 4 diodes arranged in a bridge configuration to convert both half-cycles of AC into DC.

What does the term 'gain' mean in the context of an amplifier?

Answer: The ratio of output signal amplitude to input signal amplitude

Gain is the ratio of output to input (voltage, current, or power), indicating how much the amplifier increases the signal.

A fuse is rated at 5 amps. If the circuit draws 7 amps, what will happen?

Answer: The fuse will blow, opening the circuit

When current exceeds the fuse rating, the fuse element melts and opens the circuit, protecting the wiring and components.

What is the function of an oscilloscope in electronics testing?

Answer: To display voltage waveforms as a function of time

An oscilloscope displays voltage versus time on a screen, allowing technicians to visualize signal shape, frequency, and amplitude.

Which law states that the total current entering a junction equals the total current leaving the junction?

Answer: Kirchhoff's Current Law

Kirchhoff's Current Law (KCL) states that charge is conserved at any node, so all currents entering must equal all currents leaving.