Maharashtra HSC Electronics and Hardware Technician (NSQF E5) flashcards

35 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ohm's law

The current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance: V = I × R, with V in volts, I in amperes and R in ohms.

Kirchhoff's voltage law

Around any closed loop of a circuit, the algebraic sum of all voltage rises and drops equals zero. It follows from conservation of energy and is used to solve loop currents.

Parallel resistance formula

For resistors in parallel, the reciprocal of total resistance equals the sum of reciprocals: 1/RT = 1/R1 + 1/R2 + ... The total is always smaller than the smallest branch resistance.

RMS value

The effective value of an AC waveform that produces the same heating as an equal DC value. For a sine wave, RMS = peak ÷ √2, approximately 0.707 times the peak value.

Resistor colour code

Bands give digit, digit, multiplier and tolerance: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9; gold ±5%, silver ±10%.

Zener diode regulation

A Zener diode operated in reverse breakdown holds a nearly constant voltage across itself. It is always used with a series resistor to limit current and dissipate excess voltage.

BJT current gain beta

Beta (hFE) is the ratio of collector current to base current in the active region: IC = β × IB. Typical small-signal transistors have beta between 50 and 400.

LED series resistor

The resistor value is (supply voltage minus LED forward voltage) divided by the desired LED current. It limits current because an LED has almost no internal resistance.

MOSFET gate sensitivity

The insulated gate has a very thin oxide that is easily punctured by electrostatic discharge. Gate charge is voltage-controlled, so almost no steady gate current flows.

Good solder joint

A shiny, smooth, concave fillet that wets both pad and lead, with no cracks or voids. Dull, grainy or ball-shaped joints indicate cold soldering and unreliable connection.

Desoldering braid

A flux-impregnated copper wick placed on the joint and heated with the iron; capillary action draws molten solder into the braid, clearing pads for component removal.

Reflow profile stages

Preheat, soak, reflow and cooling. The peak temperature must exceed the solder liquidus briefly without overheating components; ramp rates are kept moderate to avoid thermal shock.

Solder bridge defect

An unintended solder connection between two adjacent pads or pins, causing a short circuit. It is removed with desoldering braid and flux, then reinspected under magnification.

De Morgan's theorems

The complement of a product equals the sum of complements, and the complement of a sum equals the product of complements: (A·B)' = A' + B' and (A + B)' = A'·B'.

Universal gates

NAND and NOR gates are called universal because any logic function, including AND, OR and NOT, can be built using only one of these gate types.

D flip-flop

A clocked storage element that copies the D input to the Q output on the active clock edge. It is the basic building block of registers and shift registers.

Microcontroller versus microprocessor

A microcontroller integrates CPU, memory, timers and I/O peripherals on one chip for embedded control; a microprocessor is mainly a CPU and needs external memory and interfaces.

Ammeter connection

An ammeter is connected in series with the circuit branch whose current is measured. It must have very low resistance so that it does not alter the current being measured.

Oscilloscope time base

The time/division control sets the horizontal sweep. Signal period equals horizontal divisions occupied by one cycle multiplied by the time/div setting.

Diode test mode

The multimeter applies a small voltage and displays the forward drop. A good silicon diode reads about 0.4 to 0.8 V one way and open circuit the other way.

Multimeter accuracy specification

Accuracy is stated as plus or minus a percentage of reading plus a number of least-significant counts, for example ±(0.5% + 2 digits), over a stated temperature range.

POST beep codes

Audible patterns produced by the motherboard during power-on self-test when a critical component such as RAM, CPU or graphics fails, guiding the technician to the faulty part.

ATX 24-pin connector

The main motherboard power connector carrying +3.3 V, +5 V, +12 V, −12 V, +5 V standby and power-good signals. It is keyed and must never be forced.

Substitution troubleshooting

Replacing a suspected component with a known-good one to confirm the fault. It isolates the defective part quickly when test instruments cannot reach the circuit node.

Bridge rectifier

Four diodes arranged so both half-cycles of AC are rectified into DC. Output ripple frequency is twice the mains frequency, and no centre-tapped transformer is needed.

Three-terminal regulator 7805

A fixed linear regulator giving +5 V output. Input must be about 2 to 3 V higher than output, and a heat sink is needed when dissipation is large.

Li-ion CC/CV charging

Charging first at constant current until the cell reaches about 4.2 V, then at constant voltage while current tapers. A protection circuit prevents overcharge and over-discharge.

UPS VA rating

Apparent power the UPS can deliver: VA = watts divided by load power factor. A 600 VA unit at 0.6 power factor supports roughly 360 W of real load.

ESD wrist strap

A conductive band worn on the wrist, connected to ground through a 1 MΩ resistor. It slowly bleeds static charge while limiting current for user safety.

Electrical fire extinguisher

Class C or electrical fires require CO2 or dry-powder extinguishers. Water and foam conduct electricity and must never be used on live electrical equipment.

E-waste segregation

Separating batteries, circuit boards, CRTs and lamps from general waste and routing them to authorised recyclers, because they contain lead, mercury and other hazardous substances.

IPC-A-610 classes

Acceptance standards for electronic assemblies: Class 1 general electronics, Class 2 dedicated service products, Class 3 high-reliability products where continued performance is critical.

Calibration traceability

An instrument's readings are compared with a reference standard whose accuracy is documented back to a national standard, with certificate number and next-due date recorded.

Break-even quantity

The number of units or services at which total revenue equals total cost: fixed cost divided by the difference between selling price and variable cost per unit.

STAR interview answer

A structured reply describing the Situation, the Task required, the Action taken and the Result achieved. It gives concrete evidence of skills during a job interview.