Right Circular Cylinder vs Hollow Circular Cylinder

 

🔷 Right Circular Cylinder vs Hollow Circular Cylinder

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Right Circular Cylinder

✅ Definition:

A right circular cylinder is a solid 3D shape having:

Two equal circular bases

One curved surface
The axis is perpendicular (90°) to the base

👉 “Right” means the cylinder stands straight.

📦 Practical Examples:

Water bottle

Gas cylinder
Pipe (solid model)
Chalk piece
Candle

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📐 Important Formulas

Let radius = r
Height = h

1. Volume = πr²h

2. Curved Surface Area (CSA) = 2πrh

3. Total Surface Area (TSA) = 2πrh + 2πr²

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 Hollow Circular Cylinder

✅ Definition:

A hollow circular cylinder has:

An outer radius (R)

An inner radius (r)
Empty space inside

👉 It is like a pipe.

📦 Practical Examples:

Water pipe

Straw
Hollow iron rod
PVC pipe

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📐 Important Formulas

Let:

Outer radius = R

Inner radius = r
Height = h

1. Volume of material = πh(R² − r²)

2. Curved Surface Area (outer) = 2πRh

3. Curved Surface Area (inner) = 2πrh

4. Total Surface Area = 2πh(R + r) + 2π(R² − r²) 

Comparison Table

Feature	Right Circular Cylinder	Hollow Circular Cylinder
Structure	Solid	Empty inside
Number of radii	1 radius (r)	2 radii (R and r)
Volume	πr²h	πh(R² − r²)
Example	Candle	Pipe
Use in real life	Storage (water tank)	Transport of liquids

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 Simple Practical Understanding

🧃 Cold Drink Can

This is a right circular cylinder (solid shape).

🚰 Water Pipe

This is a hollow circular cylinder because water passes through inside.

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 Important Exam Points

✔ Always check if inner radius is given → Then it is hollow
✔ Volume difference formula commonly asked
✔ CSA of hollow cylinder includes both inner & outer curved areas
✔ π value used:

• 22/7 (if radius multiple of 7)

• 3.14 (decimal questions