Explanation

Mercury has two different critical temperatures depending on the phenomenon:

Its thermodynamic critical temperature for a substance to become a supercritical fluid is approximately 1,476.9 °C (1,750.1 K),

While its superconducting critical temperature, below which it loses all electrical resistance, is about 4.15 K. 

Explanation

A DIAC is an AC switch.

It conducts in both directions once a certain breakdown voltage is reached.

This making it useful for switching applications in AC circuits.

Explanation

If A · B = 0, it means the vectors A and B are perpendicular.

The magnitude of the cross product is:

|A × B| = |A||B|sinθ

For perpendicular vectors, θ = 90°, so sin(90°) = 1

⇒ |A × B| = AB × 1 = AB

Explanation

 A · A = |A||A|cos(0) = A² (since cos 0 = 1)  

   - This gives the magnitude squared of the vector.  

Explanation

Resistivity is a measure of how strongly a material opposes the flow of electric current.

Here's a general classification based on resistivity (in Ω-cm):

$10^5$ and 10 ^9 Ω-cm, it is classified as an insulator because it resists the flow of electric current very strongly.

Explanation

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature.

This allows for highly efficient electrical conduction and magnetic field exclusion.

Explanation

Mercury is used as a thermometric fluid because it has several ideal properties:

1. High Boiling Point (B.P)

   • Mercury doesn't evaporate easily, which makes it suitable for measuring high temperatures.

2. Low Freezing Point (not high M.P)

   • Mercury has a low melting point (−38.83°C), which helps in measuring low temperatures, though this limits it in very cold environments.

3. Stable and Uniform Coefficient of Expansion

   • Mercury expands uniformly with temperature, which gives accurate and consistent readings.

4. Visibility and Non-wettability

   • Mercury is shiny and opaque, so it's easy to see in a glass tube.

   • It doesn't stick to glass, which keeps the readings clean and precise.

Explanation

 The phenomenon responsible for light propagation in optical fibers is total internal reflection.

In an optical fiber, light travels through the core by repeatedly reflecting off the core–cladding boundary.

This happens when light hits the boundary at an angle greater than the critical angle, causing total internal reflection instead of refraction.

This keeps the light trapped inside the core, allowing it to travel long distances with minimal loss.

Explanation

A tuning fork is specifically designed to vibrate at a specific frequency,

And it resonates when struck, producing a sound wave at that particular frequency

Explanation

Solution for Total Time of Flight of a Projectile:

Given:  

- Initial velocity = u  

- Angle of projection = θ  

- Acceleration due to gravity = g  

When a projectile is launched, it moves upward and then comes back down under gravity.

- The vertical component of velocity = u sin θ  

- The time to reach the highest point (where vertical velocity = 0) is:  

  t = (u sin θ) / g  

- Total time of flight is twice the time to reach the highest point (because time going up = time coming down), so:  

  T = 2 × (u sin θ) / g = (2u sin θ) / g