GK: Class 12 General Q&A · Page 82
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What is 120 volts at 80 ohms?
Using Ohm's Law (I = V ÷ R), 120 volts applied to 80 ohms produces 1.5 amperes of current (120V ÷ 80Ω = 1.5A). This might represent a small heating element or light bulb operating on standard household voltage.
- GeneralClass 12All
What are the 3 formulas of power?
The three power formulas in electrical circuits are: P = V × I (power = voltage × current) P = I² × R (power = current squared × resistance) P = V² ÷ R (power = voltage squared ÷ resistance) These derive from combining Ohm's Law with the basic power equation and allow you to calculate power when you know different combinations of V, I, and R.</p
- GeneralClass 12All
Is electrical power AC or DC?
Electrical power exists in both AC and DC forms. DC power is constant and unidirectional, used in batteries and electronic devices. AC power varies sinusoidally and is used for power distribution because it's more efficient to transmit over long distances. The power formula P = V × I applies to both, though AC power calculations may involve additional factors like power factor.
- GeneralClass 12All
What is the SI unit of power?
The SI unit of power is the watt (W), named after Scottish engineer James Watt. One watt equals one joule of energy per second, or in electrical terms, one volt-ampere (1W = 1V × 1A). Common multiples include kilowatts (1000W) for household appliances and megawatts (1,000,000W) for large-scale power systems.
- GeneralClass 12All
What is a wavelength?
Wavelength is the distance between two consecutive identical points on a wave, such as from one crest to the next crest or from one trough to the next trough. Measured in meters (m), nanometers (nm), or other length units, wavelength represents the spatial period of a wave. It's a fundamental property that determines many characteristics of waves, including their energy and how they interact with matter. For example, visible light wavelengths range from about 400 nm (violet) to 700 nm (red).<
- GeneralClass 12All
Why is it called wavelength?
The term "wavelength" combines "wave" and "length" to describe the physical distance over which a wave's shape repeats. The name intuitively reflects what it measures: the length of one complete wave cycle in space. This terminology was adopted because it clearly describes the spatial extent of a single oscillation, making it easy to understand and communicate in scientific contexts.
- GeneralClass 12All
What is wavelength and frequency?
Wavelength (λ) and frequency (f) are inversely related properties of waves. Wavelength is the spatial distance between repeating wave patterns, while frequency is the number of wave cycles that pass a point per second, measured in Hertz (Hz). They're connected by the equation v = fλ, where v is wave velocity. When frequency increases, wavelength decreases, and vice versa. For instance, radio waves have low frequencies and long wavelengths, while gamma rays have high frequencies
- GeneralClass 12All
How to calculate wavelength?
To calculate wavelength, use the formula λ = v/f, where λ (lambda) is wavelength, v is wave velocity, and f is frequency. For electromagnetic waves in vacuum, use λ = c/f, where c = 3 × 10⁸ m/s (speed of light). For example, if a wave has a frequency of 100 Hz and travels at 340 m/s (speed of sound), the wavelength is λ = 340/100 = 3.4 meters. You can also calculate wavelength from energy using λ = hc/E, where h is Planck's constant and E is photon ene
- GeneralClass 12All
How to find wavelength class 9?
For class 9 level, wavelength is found using the basic formula λ = v/f. First, identify the wave's velocity (v) and frequency (f). For sound waves in air at room temperature, use v ≈ 340 m/s. For light waves, use v = 3 × 10⁸ m/s. Divide the velocity by the frequency to get wavelength. For example, if a sound wave has frequency 680 Hz, then λ = 340 m/s ÷ 680 Hz = 0.5 m. Remember to keep units consistent throughout your calculation.
- GeneralClass 12All
What symbol is λ?
λ (lambda) is the 11th letter of the Greek alphabet, written in lowercase. In physics, it's the standard symbol for wavelength. The uppercase version (Λ) is used for different quantities. Lambda appears frequently in scientific notation because Greek letters provide a universal symbolic language that transcends language barriers, making scientific communication more efficient and reducing confusion with other variables.
- GeneralClass 12All
Is 1 lambda equal to frequency?
No, one wavelength (1λ) does not equal frequency. Wavelength is a distance measurement, while frequency is a time-based measurement (cycles per second). They're related but not equal. The relationship is f = v/λ, where dividing velocity by wavelength gives frequency. For example, if λ = 2 m and v = 340 m/s, then f = 170 Hz. These are fundamentally different properties that together with velocity describe wave characteristics.
- GeneralClass 12All
Is frequency equal to wavelength?
No, frequency is not equal to wavelength they are inversely related. Frequency (f) measures cycles per second, while wavelength (λ) measures distance per cycle. The relationship is v = fλ, meaning as frequency increases, wavelength decreases proportionally if velocity remains constant. They are different physical quantities with different units: frequency in Hertz (Hz) and wavelength in meters (m). However, knowing one allows you to calculate the other if you know the wave's spe
- GeneralClass 12All
What is the wavelength λ of the wave?
The wavelength λ of any specific wave is determined by its frequency and propagation speed using λ = v/f. For electromagnetic waves in vacuum, λ = c/f where c = 3 × 10⁸ m/s. To find a wave's wavelength, identify what type of wave it is, determine its frequency, know the medium it travels through (which affects velocity), then apply the appropriate formula. The resulting wavelength tells you the spatial period of that particular wave.
- GeneralClass 12All
What is the value of λ?
Lambda (λ) doesn't have a single fixed value it varies depending on the wave being measured. Each wave has its own wavelength based on its frequency and velocity. For example, visible light ranges from λ = 400 nm (violet) to 700 nm (red), while radio waves can have wavelengths from millimeters to kilometers. To find a specific λ value, you need to know the wave's properties and calculate using λ = v/f or other relevant formulas.
- GeneralClass 12All
What is the meaning of v = fλ?
The equation v = fλ is the fundamental wave equation relating velocity (v), frequency (f), and wavelength (λ). It states that wave speed equals frequency multiplied by wavelength. This means waves with higher frequency must have shorter wavelengths if speed is constant, and vice versa. This relationship applies to all waves sound, light, water waves, and more. It's crucial for understanding wave behavior, designing antennas, analyzing spectra, and countless applications in physi
- GeneralClass 12All
How long is a 30 Hz wavelength?
For a 30 Hz wave, wavelength depends on the medium. In air (sound), using v = 340 m/s: λ = 340/30 ≈ 11.3 meters. For electromagnetic waves: λ = (3 × 10⁸)/30 = 10,000,000 meters or 10,000 km. This demonstrates that low-frequency waves have very long wavelengths. A 30 Hz sound wave would be a deep bass tone, while a 30 Hz radio wave would fall in the extremely low frequency (ELF) range used for submarine communication.
- GeneralClass 12All
How to calculate lambda?
Lambda (λ) represents wavelength and is calculated using λ = v/f for mechanical waves or λ = c/f for electromagnetic waves. Alternative formulas include λ = hc/E (from energy, where h = 6.626 × 10⁻³⁴ J·s) and λ = h/p (de Broglie wavelength, where p is momentum). Choose the appropriate formula based on available information. Always ensure units are compatible: velocity in m/s, frequency in Hz, energy in Joules, and the result will be wavelen
- GeneralClass 12All
How to calculate wavelength with only distance?
If you only have distance information, you need additional data to find wavelength. You must know either: (1) how many complete waves fit in that distance (wavelength = distance/number of waves), (2) the frequency and wave speed (λ = v/f), or (3) two consecutive similar points in the wave pattern. Simply having a distance value alone is insufficient; wavelength requires understanding the wave's repeating pattern or having related wave properties.
- GeneralClass 12All
How to calculate wavelength to frequency?
To convert wavelength to frequency, rearrange the wave equation to f = v/λ. For electromagnetic waves, use f = c/λ where c = 3 × 10⁸ m/s. For example, if light has a wavelength of 500 nm (500 × 10⁻⁹ m), its frequency is f = (3 × 10⁸)/(500 × 10⁻⁹) = 6 × 10¹⁴ Hz. This calculation is essential in spectroscopy, telecommunications, and understanding electromagnetic radiation properties.
- GeneralClass 12All
Why is resistance called ohm?
Resistance is measured in ohms to honor Georg Simon Ohm (1789-1854), the German physicist who discovered the relationship between voltage, current, and resistance in 1827. The symbol Ω (Greek letter omega) represents the ohm unit in his recognition.