Explanation

When a substance is cooled slowly, only a limited number of nucleation sites are formed.

As a result, larger crystals are produced.

The better crystals tend to be obtained on slow cooling than on rapid cooling

• because rapid cooling induces the formation of many nucleation sites
• fast cooling yields small crystals.
  

Explanation

Ozone formula: O3

The stratospheric ozone layer is Earth's “sunscreen”  protecting living things from too much ultraviolet radiation from the sun.

Oxygen layer in the atmosphere

Ozone protects us from the harmful ultraviolet radiation of the sun.

The ozone layer lies approximately 15-40 kilometers (10-25 miles) above the Earth's surface, in the stratosphere.

The ozone layer is depleting: Air pollution

ND17-7-2023

Explanation

- When an object falls through a fluid (like air), it accelerates until forces balance.

- At terminal velocity:

  - Air resistance = Weight (mg)

  - Net force = 0

  - So, acceleration = 0

- Common in skydiving and falling raindrops.

Explanation

- Lead (Pb) is a stable element → its common isotope is not radioactive.

- Radium (Ra), Radon (Rn), and Uranium (U) are radioactive.

- Radioactive elements emit alpha, beta, or gamma radiation.

Explanation

. Ohmmeter (for measuring resistance):

- Measures resistance directly in ohms (Ω).

- Faster and more efficient than a voltmeter + ammeter combination.

- Used in electronics to test resistors and circuit continuity.

Explanation

Digital multimeters are measuring instruments that can measure quantities:

Such as voltage, current, and resistance.

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Explanation

 Y's son → let's call him A

- A's son → B

- X is the brother of B

So, X and B are sons of Y’s grandson, making X Y’s great-grandson

BUT the best possible relationship in options:

- X is the grandson of Y.

Explanation

Let's look at the pattern:

- 6 → 13: +7  

- 13 → 28: +15  

- 28 → ?

Check the difference pattern:  

+7, +15  

Seems to be doubling and adding 1:  

7 → 15 → next would be 31

So:  

28 + 31 = 59

Explanation

Given string:

531875156352095351025871533501355325

We’re looking for “5 followed by 3” (i.e., "53")

Let’s count all occurrences of "53" in the string:

Scan the number:

→ 531875156352095351025871533501355325

Occurrences of "53":

1. 531   

2. 535   

3. 533 

4. 535   

5. 532 

Total = 5

Explanation

- A body becomes positively charged when it loses electrons (not gains protons).

- Protons cannot move during rubbing, but electrons can.

- Rubbing transfers electrons from one object to another.