BSF HC RO/RM flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Number series shortcut
- Compute first differences; if constant, the series is arithmetic. If differences form a pattern (increasing, alternating, prime), extend that pattern. Check squares and cubes before assuming a random rule.
- Blood relation tree
- Draw vertical lines for parent-child and horizontal lines for spouse or sibling. Mark gender only when stated. Answer by tracing the shortest path between the two named persons.
- Syllogism validity test
- A conclusion is valid only if it is true in every possible Venn diagram of the premises. 'All A are B' does not reverse; 'some A are B' does reverse to 'some B are A'.
- Successive percentage change
- Net change for a% followed by b% equals a + b + (ab)/100. Two successive 10% increases give 21%, not 20%, because the second applies to the raised value.
- Compound interest formula
- Amount A = P(1 + R/100)^T for annual compounding. Compound interest = A − P. For two years, CI exceeds simple interest by P(R/100)².
- Speed unit conversion
- Multiply km/h by 5/18 to get m/s; multiply m/s by 18/5 to get km/h. Relative speed adds for opposite directions and subtracts for same-direction travel.
- Time and work formula
- If A alone takes a days and B alone b days, together they take ab/(a + b) days. This follows from 1/a + 1/b = 1/t, where t is the combined time.
- Alligation rule
- Ratio of quantities mixed = (mean price − cheaper price) : (dearer price − mean price). Applies to mixtures, averages and profit-loss blending problems.
- Fundamental Duties
- Added by the 42nd Constitutional Amendment in 1976 on Swaran Singh Committee advice, listed in Article 51A under Part IVA. They are moral obligations, not directly enforceable by courts.
- BSF role and motto
- Border Security Force, raised in 1965, guards India's land borders with Pakistan and Bangladesh under the Ministry of Home Affairs. Its motto is 'Jeevan Paryant Kartavya'.
- Tropic of Cancer in India
- Passes through eight states, from Gujarat and Rajasthan in the west through Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Tripura and Mizoram in the east.
- Chandrayaan-3 mission
- ISRO mission whose lander Vikram touched down near the Moon's south pole in August 2023, making India the first country to land in that region.
- Active to passive voice
- Move the object to subject position, change the verb to a form of 'be' plus past participle, and add the original subject after 'by'. Keep the tense unchanged.
- Subject-verb agreement rule
- A singular subject takes a singular verb. In 'one of the + plural noun', the verb agrees with 'one', so it stays singular, as in 'one of the boys is here'.
- Prepositions of time
- Use 'in' for months, years and seasons; 'on' for days and dates; 'at' for clock times. Use 'since' with a starting point and 'for' with a duration.
- Idiom: at the drop of a hat
- Means immediately and without hesitation. Idiom questions are best solved by substituting the phrase into the sentence and checking which meaning fits the context.
- संधि क्या है
- दो वर्णों के मेल से होने वाले परिवर्तन को संधि कहते हैं। यह स्वर, व्यंजन और विसर्ग तीन प्रकार की होती है, जैसे विद्या + आलय = विद्यालय।
- तत्पुरुष समास
- जिस समास में उत्तर पद प्रधान हो और पूर्व पद गौण हो, उसे तत्पुरुष कहते हैं। उदाहरण: राजपुत्र अर्थात राजा का पुत्र।
- मुहावरा: नौ दो ग्यारह होना
- इस मुहावरे का अर्थ है भाग जाना या चुपचाप खिसक जाना। मुहावरे का अर्थ शब्दों के शाब्दिक अर्थ से भिन्न, लाक्षणिक होता है।
- कारक विभक्ति चिह्न
- कर्ता के साथ 'ने', कर्म के साथ 'को', करण के साथ 'से' या 'के द्वारा', संप्रदान के साथ 'के लिए' और अधिकरण के साथ 'में' या 'पर' चिह्न लगता है।
- Ohm's law and power
- Voltage equals current times resistance (V = IR). Power equals VI, also I²R or V²/R. In series, resistances add; in parallel, reciprocals add.
- Wavelength formula
- Wavelength in metres equals 300 divided by frequency in MHz. So 30 MHz corresponds to 10 metres and 300 MHz to 1 metre, using light speed 3 × 10⁸ m/s.
- AM versus FM
- AM varies carrier amplitude and needs wider spacing but travels far on lower bands. FM varies carrier frequency, resists noise better, and is used for VHF local communication.
- Half-wave dipole length
- Length in metres approximately equals 143 divided by frequency in MHz. A 7 MHz dipole is therefore about 20 metres long, split into two equal legs.
- VSWR meaning
- Voltage Standing Wave Ratio measures antenna match. A value near 1:1 means almost all power radiates; a high ratio means reflected power, poor range and possible transmitter damage.
- Radiotelephony prowords
- ROGER means received correctly, OVER means reply expected, OUT means end of contact with no reply, WILCO means will comply, and MAYDAY signals grave and imminent danger.
- Skywave propagation
- HF signals refract off the ionosphere and return to earth beyond the horizon, enabling long-distance communication. It works best at night on lower HF bands.
- Memory unit conversion
- One byte is eight bits. One kilobyte is 1024 bytes, one megabyte is 1024 kilobytes, one gigabyte is 1024 megabytes, and one terabyte is 1024 gigabytes.
- IPv4 address structure
- IPv4 uses 32 bits written as four decimal octets from 0 to 255, for example 192.168.1.1. IPv6 uses 128 bits and is written in hexadecimal groups.
- Private IP ranges
- Non-routable private blocks are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. They need NAT to reach the public internet.
- OSI model layers
- Seven layers from bottom: Physical, Data Link, Network, Transport, Session, Presentation, Application. IP works at Network, TCP and UDP at Transport, HTTP at Application.
- Common protocol ports
- HTTP uses 80, HTTPS 443, FTP 21, SSH 22, Telnet 23, SMTP 25 and DNS 53. Port numbers identify which service handles incoming traffic on a host.