What are the differences between plane angle and solid angle?
Plane Angle:
- Formed by the intersection of two lines.
- It is two-dimensional.
- SI unit is radian (rad).
Solid Angle:
- Formed by the intersection of three or more planes at a common point.
- It is three-dimensional.
- SI unit is steradian (sr).
[viii] Answer in detail.
List out the base quantities with their units.
The International System of Units (SI) defines seven base quantities, each with a corresponding unit. These quantities and their units are fundamental to scientific measurement and are used globally. Here is the list:
Length
Unit: Meter (m)
Definition: The meter is defined as the distance traveled by light in a vacuum in 1/299,792,458 seconds.
Mass
Unit: Kilogram (kg)
Definition: The kilogram is defined by taking the fixed numerical value of the Planck constant, h, to be 6.62607015 x 10⁻³⁴ when expressed in the unit J·s, which is equal to kg·m²·s⁻¹.
Time
Unit: Second (s)
Definition: The second is defined by taking the fixed numerical value of the cesium frequency Δν₃, the unperturbed ground-state hyperfine transition frequency of the cesium-133 atom, to be 9,192,631,770 Hz.
Electric Current
Unit: Ampere (A)
Definition: The ampere is defined by taking the fixed numerical value of the elementary charge, e, to be 1.602176634 x 10⁻¹⁹ when expressed in the unit C, which is equal to A·s.
Temperature
Unit: Kelvin (K)
Definition: The kelvin is defined by taking the fixed numerical value of the Boltzmann constant, k, to be 1.380649 x 10⁻²³ when expressed in the unit J·K⁻¹, which is equal to kg·m²·s⁻²·K⁻¹.
Amount of Substance
Unit: Mole (mol)
Definition: The mole is defined by taking the fixed numerical value of the Avogadro constant, N_A, to be 6.02214076 x 10²³ when expressed in the unit mol⁻¹.
Luminous Intensity
Unit: Candela (cd)
Definition: The candela is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 x 10¹² Hz, K_cd, to be 683 when expressed in the unit lm·W⁻¹, which is equal to cd·sr·W⁻¹, or cd·sr·kg⁻¹·m⁻²·s³.
Write a short note on different types of clocks.
Clocks are devices used to measure and display time. Over the years, various types of clocks have been developed, each with different mechanisms and features. Here are some common types:
Analog Clocks
Description: These clocks have a traditional face with hour, minute, and sometimes second hands that move in a circular motion. The hands point to numbers or markers around the clock face.
Mechanism: Analog clocks can be mechanical (wound by hand or powered by a weight) or electronic (powered by batteries with a quartz crystal oscillator).
Digital Clocks
Description: Digital clocks display time in numerical form, typically using LCD or LED screens. They often provide a 12-hour or 24-hour time format.
Features: Many digital clocks include additional features such as alarms, calendars, temperature displays, and timers.
Mechanism: These clocks are usually powered by batteries or electricity and use electronic circuits to keep time accurately.
Quartz Clocks
Description: Quartz clocks are highly accurate and commonly used in households and workplaces. They may have either analog or digital displays.
Mechanism: These clocks use a quartz crystal oscillator to keep time. When an electric current is applied to the crystal, it vibrates at a precise frequency, which is used to regulate the timekeeping mechanism.
Atomic Clocks
Description: Atomic clocks are the most accurate timekeeping devices available. They are used in scientific research, global positioning systems (GPS), and international time distribution services.
Mechanism: These clocks measure the vibrations of atoms (typically cesium or rubidium) to maintain extremely precise time. Atomic clocks are accurate to within a few billionths of a second per day.
Mechanical Clocks
Description: Mechanical clocks include traditional pendulum clocks and watches that require winding. They have intricate internal gears and springs.
Mechanism: These clocks operate based on the mechanical movement of gears and springs. A wound spring provides the energy that drives the gears and moves the clock’s hands.
Smart Clocks
Description: Smart clocks are modern devices that integrate with smart home systems. They offer various functionalities such as voice control, internet connectivity, and synchronization with other smart devices.
Features: In addition to displaying time, smart clocks can show weather updates, control smart home devices, play music, and more.
