Maharashtra SSC Electronics and Hardware Pre-Voc/NSQF flashcards

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

Ohm's law

Current through a conductor is directly proportional to voltage across it and inversely proportional to resistance, written V = I × R, with V in volts, I in amperes and R in ohms.

Resistor colour code

Four bands give digit, digit, multiplier and tolerance. Brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9; gold means plus or minus five percent.

Parallel resistance rule

In a parallel circuit every branch has the same voltage and total resistance is found from one over R total equals the sum of one over each branch resistance.

Voltmeter connection

A voltmeter is connected in parallel across the component being measured and must have very high internal resistance so it draws almost no current from the circuit.

Ammeter connection

An ammeter is connected in series with the load and has very low internal resistance, so it does not drop voltage or disturb the current being measured.

Continuity test

With power removed, a multimeter on continuity or low ohm range beeps for a closed path and shows overload for an open circuit, confirming wiring and switch operation.

Oscilloscope volts per division

The vertical scale control sets how many volts each grid square represents; multiplying the displayed height in divisions by this setting gives the signal amplitude.

PN junction forward bias

When the anode is made positive relative to the cathode, the depletion region narrows and current flows after about 0.7 volts for silicon diodes.

Bridge rectifier ripple

A full-wave bridge rectifier converts both half cycles of the AC input, so the output ripple frequency is twice the mains frequency, 100 hertz for 50 hertz supply.

Zener diode regulation

A Zener diode operated in reverse breakdown holds a nearly constant voltage; a series resistor drops the difference and limits current through the diode and load.

Transistor current gain

Beta or hFE equals collector current divided by base current in the active region, showing how a small base current controls a much larger collector current.

Cold solder joint

A dull, grainy, ball-shaped joint formed when the joint did not reach soldering temperature or moved while cooling; it gives intermittent, high-resistance connection.

Rosin flux function

Rosin flux chemically removes oxide film from pads and leads during soldering so molten solder wets the metal and forms a smooth, reliable joint.

Desoldering braid

A fine copper braid placed over a joint and heated with the iron; capillary action draws molten solder into the braid, clearing pads and removing bridges.

Component placement order

On a PCB, fit low-profile parts such as resistors and diodes first, then sockets and integrated circuits, and tall electrolytic capacitors and connectors last.

Mains wire colour code

In Indian practice the phase conductor is red or brown, neutral is black or blue, and the protective earth is green or green with yellow stripes.

Megger insulation test

An insulation resistance tester applies a high DC voltage between live conductors and earth; a healthy installation reads in megohms, while a low reading indicates leakage.

Thermal paste purpose

A thin layer of thermally conductive paste fills microscopic air gaps between the CPU and heatsink, improving heat transfer from the processor to the cooler.

Motherboard standoffs

Metal or plastic spacers screwed into the case that hold the motherboard clear of the chassis and prevent short circuits between solder joints and metal.

BIOS and UEFI

Firmware stored on the motherboard that runs the power-on self-test, initialises hardware and loads the operating system; settings are entered with Del or F2 at boot.

Byte and bit relation

One byte consists of eight bits; storage units then step by 1024, so one kilobyte is 1024 bytes and one megabyte is 1024 kilobytes.

RAM versus ROM

RAM is volatile working memory that loses contents when power is removed, while ROM is non-volatile and retains firmware permanently or until reprogrammed.

Hexadecimal number system

A base-16 number system using digits zero to nine and letters A to F, where A equals ten and F equals fifteen; widely used to write memory addresses.

DHCP function

Dynamic Host Configuration Protocol automatically supplies an IP address, subnet mask, default gateway and DNS server to a device joining the network.

Private IP address ranges

Ranges reserved for local networks are 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255 and 192.168.0.0 to 192.168.255.255.

DNS resolution

The Domain Name System translates human-readable names such as a website address into numeric IP addresses that computers use to route traffic.

Fan capacitor fault

A ceiling or table fan that hums but does not rotate usually has a failed run capacitor; a good capacitor shows a rising ohm reading as it charges.

SMPS fuse check

In a switched-mode power supply, a blown mains fuse points to a short downstream, commonly the bridge rectifier or switching transistor, which must be tested before replacing the fuse.

Electric shock first aid

Switch off the supply or separate the victim using dry insulating material, call emergency help, and begin cardiopulmonary resuscitation if breathing or pulse has stopped.

RCCB purpose

A residual current circuit breaker detects earth leakage current, typically tripping at 30 milliamperes, and protects people from fatal electric shock.

Lockout tagout

A safety procedure in which the power source is switched off, locked and tagged, and the circuit is verified dead before maintenance work begins.

Vernier caliper least count

The smallest measurement a vernier caliper can read, calculated as one main scale division divided by the number of vernier divisions, commonly 0.02 millimetres.

Break-even quantity

The number of units or jobs a business must complete to cover all costs, calculated as fixed cost divided by selling price minus variable cost per unit.

Udyam registration

The Indian government portal that registers micro, small and medium enterprises and provides access to credit, subsidy and tender-preference schemes.

E-waste recycling

Discarded electronics containing lead, mercury and cadmium must be handed to authorised recyclers rather than mixed with household waste or burned informally.

Job sheet record

A document listing customer details, reported fault, diagnosis, parts replaced, charges and customer signature, used for warranty and business records.

APIPA address meaning

An address in the 169.254 range assigned by Windows when no DHCP server responds, indicating the device could not obtain a valid network configuration.

T568B wiring order

Ethernet pin order: white-orange, orange, white-green, blue, white-blue, green, white-brown, brown; both ends wired the same make a straight-through cable.

Series bulb test

A filament lamp connected in series with a device under repair limits current, so a short circuit lights the bulb brightly instead of destroying components.

Microwave capacitor hazard

The high-voltage capacitor in a microwave oven retains a lethal charge after power-off and must be discharged through a resistor before any servicing.