General Q&A for Class 12 · Page 196
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
How Does Snell's Law Explain Mirages?
Mirages occur due to Snell's Law when light passes through air layers of different temperatures and densities. On hot days, air near the ground is much hotter and less dense than air above it, creating a gradient in refractive index. Light from the sky continuously refracts as it passes through these layers, eventually bending so much that it curves upward. This makes it appear as if there's a reflection of the sky on the ground, which looks like water. Snell's Law governs each small refracti
- GeneralClass 12All
What is an Example of Snell's Law?
A common example is a straw in a glass of water appearing bent at the water's surface. The light reflecting off the submerged portion of the straw refracts as it exits the water and enters the air, making the straw appear disconnected or bent. Another example is a swimming pool appearing shallower than it actually is because light from the pool bottom refracts as it exits the water, reaching our eyes at a different angle.
- GeneralClass 12All
How Many Types of Laws of Refraction Are There?
There are primarily two laws of refraction, though they're sometimes subdivided into more specific statements. The two main laws are: (1) the geometric law stating all rays lie in one plane, and (2) Snell's Law describing the mathematical relationship between angles and refractive indices. Some classifications include additional aspects like the principle of reversibility or specific cases like total internal reflection.
- GeneralClass 12All
How much unit is 1 amp?
Amperes (amps) measure current, while units (kWh) measure energy consumption they're different uantities. To convert amps to units, you need voltage and time: Units = (Volts × Amps × Hours) ÷ 1000. For example, at 120 volts: 1 amp for 1 hour = 0.12 units (120V × 1A × 1h ÷ 1000) 1 amp for 10 hours = 1.2 units At 240 volts: 1 amp for 1 hour = 0.24 units The unit consumption depends on b
- GeneralClass 12All
What does 20 watts mean?
20 watts means a device consumes or produces 20 joules of energy per second. Wattage indicates the rate of energy consumption or power output. For example: A 20-watt LED bulb is uite bright and energy-efficient A 20-watt phone charger can charge devices at a moderate speed Running a 20-watt device for 50 hours consumes 1 unit (kWh) of electricity Lower wattage generally means lower electricity consumption and cost. When comparing devices, low
- GeneralClass 12All
What are basic electrical formulas?
The essential basic electrical formulas include: Ohm's Law: V = I × R (Voltage = Current × Resistance) Power: P = V × I (Power = Voltage × Current) Power (alternative): P = I² × R or P = V²/R Current: I = /t (Current = Charge ÷ Time) Energy: E = P × t (Energy = Power × Time)
- GeneralClass 12All
What is 240 volt AC or DC?
240 volts is typically AC (alternating current) in most applications worldwide. It's the standard household voltage in many countries including the UK, Europe, Australia, and parts of Asia. However, 240V can also be DC in specific applications: Solar power systems with battery banks Electric vehicle charging stations Industrial DC power supplies Telecommunications euipment Unless specified otherwise, 240V usually refers to AC power.
- GeneralClass 12All
Is car battery AC or DC?
A car battery is DC (direct current). Car batteries produce a steady voltage (typically 12 volts) that flows in one direction. This DC power is used to: Start the engine (starter motor) Power lights, radio, and accessories when the engine is off Provide stable power for electronic control modules While the car battery is DC, the alternator that charges it produces AC, which is then converted to DC through a rectifier. All the electrical syste
- GeneralClass 12All
Which is stronger, AC or DC?
Neither AC nor DC is inherently "stronger"—strength depends on voltage and current, not the type. However, they have different characteristics: DC can be considered "more powerful" at the same voltage because: Delivers constant power (no zero-crossing points) More dangerous for electric shock at the same voltage Can cause continuous muscle contraction AC is "stronger" for transmission because:</
- GeneralClass 12All
What is linear momentum?
Linear momentum is a fundamental property of a moving object, defined as the product of its mass and velocity. It represents the uantity of motion an object possesses and is a vector uantity, meaning it has both magnitude and direction. The greater an object's mass or velocity, the more momentum it carries. This concept is crucial in understanding collisions, explosions, and the motion of objects in physics.
- GeneralClass 12All
What is the formula for linear momentum (P)?
The formula for linear momentum is P = mv, where P represents momentum, m is the object's mass (in kilograms), and v is its velocity (in meters per second). For example, a 2 kg ball moving at 5 m/s has a momentum of 10 kg·m/s. This simple yet powerful formula helps predict how objects will behave when forces act upon them.
- GeneralClass 12All
How do you calculate linear momentum?
To calculate linear momentum, multiply the object's mass by its velocity using the formula P = mv. First, ensure your mass is in kilograms and velocity in meters per second for SI units. Then perform the multiplication. For instance, a 1500 kg car traveling at 20 m/s has momentum of 30,000 kg·m/s. Remember that velocity includes direction, so momentum is also directional.
- GeneralClass 12All
What is the unit and dimension of linear momentum?
The SI unit of linear momentum is kilogram meter per second (kg·m/s) or euivalently, newton-second (N·s). The dimensional formula is [MLT⁻¹], where M represents mass, L represents length, and T represents time. In the CGS system, the unit is gram centimeter per second (g·cm/s). Understanding these units is essential for solving physics problems correctly.
- GeneralClass 12All
What is the dimensional formula for linear momentum in Class 11?
The dimensional formula for linear momentum is [M¹L¹T⁻¹] or simply [MLT⁻¹]. This is derived from the formula P = mv, where mass has dimension [M], and velocity has dimension [LT⁻¹]. When multiplied together, they give [MLT⁻¹]. This dimensional analysis helps verify euations and convert between different unit systems in physics problems.
- GeneralClass 12All
What is the law of linear momentum?
The law of linear momentum, also known as Newton's Second Law, states that the rate of change of momentum of an object euals the net force applied to it. Mathematically: F = ΔP/Δt or F = (mv - mu)/t. Additionally, the Law of Conservation of Linear Momentum states that in a closed system with no external forces, total momentum remains constant before and after any interaction.
- GeneralClass 12All
What speed is 3×10⁸?
3×10⁸ m/s (or 300,000,000 meters per second) is approximately the speed of light in a vacuum, denoted by 'c'. More precisely, the speed of light is 299,792,458 m/s, often rounded to 3×10⁸ m/s for calculations. This is the fastest speed possible in the universe and is fundamental to Einstein's theory of relativity.
- GeneralClass 12All
What is = mcpΔT?
= mcpΔT is the formula for calculating heat transfer at constant pressure, where is heat energy, m is mass, cp is the specific heat capacity at constant pressure, and ΔT is temperature change. This is essentially the same as = mcΔT, with cp specifically denoting constant pressure conditions. It's used to determine energy reuired to heat or cool substances.
- GeneralClass 12All
What is F·ΔT (F triangle T)?
F·ΔT or F×Δt represents impulse, the product of force and the time interval over which it acts. Impulse euals the change in momentum: F·Δt = ΔP = mv - mu. This concept is essential in understanding collisions and impacts. A large force acting for a short time (like a hammer blow) can produce the same momentum change as a small force acting for a long time.
- GeneralClass 12All
How is TCR calculated?
TCR (Temperature Coefficient of Resistance) is calculated using: TCR = (R₂ - R₁) / [R₁(T₂ - T₁)], where R₁ and R₂ are resistances at temperatures T₁ and T₂ respectively. It's expressed in per degree Celsius (1/°C) or ppm/°C. TCR indicates how much a material's electrical resistance changes with temperature, which is crucial for designing temperature sensors and precision circuits.
- GeneralClass 12All
What is Snell's Law?
Snell's Law is a fundamental principle in physics that describes how light bends when it passes from one transparent medium to another. The law states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant and eual to the ratio of the refractive indices of the two media. This bending of light, called refraction, occurs because light travels at different speeds in different materials.