krit.club logo

Heat Transfer in Nature - Conduction of Heat

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Heat is a form of energy that flows from an object at a higher temperature to an object at a lower temperature.

•

Conduction is the process of heat transfer in solids where heat is passed from one particle to the next without the actual movement of the particles from their positions.

•

For conduction to occur, two objects must be in direct contact and there must be a temperature difference between them (T1≠T2T_1 \neq T_2).

•

Conductors are materials that allow heat to pass through them easily, such as metals like Copper (CuCu), Iron (FeFe), and Aluminum (AlAl).

•

Insulators (or poor conductors) are materials that do not allow heat to pass through them easily, such as wood, plastic, glass, and air.

•

Temperature is the degree of hotness or coldness of an object, measured using a thermometer in units like Celsius (∘C^{\circ}C), Fahrenheit (∘F^{\circ}F), or Kelvin (KK).

📐Formulae

C5=F−329\frac{C}{5} = \frac{F - 32}{9}

K=C+273.15K = C + 273.15

ΔT=Thigher−Tlower\Delta T = T_{higher} - T_{lower}

💡Examples

Problem 1:

The normal temperature of the human body is 37∘C37^{\circ}C. Convert this temperature into the Fahrenheit (∘F^{\circ}F) scale.

Solution:

Using the formula C5=F−329\frac{C}{5} = \frac{F - 32}{9}, we substitute C=37C = 37: 375=F−329\frac{37}{5} = \frac{F - 32}{9} 7.4=F−3297.4 = \frac{F - 32}{9} 7.4×9=F−327.4 \times 9 = F - 32 66.6=F−3266.6 = F - 32 F=66.6+32=98.6∘FF = 66.6 + 32 = 98.6^{\circ}F

Explanation:

To convert Celsius to Fahrenheit, we multiply the Celsius value by 95\frac{9}{5} and then add 3232.

Problem 2:

A metal rod has one end at 95∘C95^{\circ}C and the other end at 42∘C42^{\circ}C. Calculate the temperature difference that drives the conduction of heat.

Solution:

The temperature difference ΔT\Delta T is calculated by subtracting the lower temperature from the higher temperature: 95−4253\begin{array}{r} 95 \\ - 42 \\ \hline 53 \end{array} So, ΔT=53∘C\Delta T = 53^{\circ}C.

Explanation:

Heat flows via conduction due to the difference in temperature between the two ends of the solid conductor.

Problem 3:

Why are the handles of cooking utensils often made of wood or plastic?

Solution:

Wood and plastic are insulators. When the metal pan is heated, heat travels through the metal via conduction. The plastic handle, being a poor conductor, does not allow this heat to pass to our hands.

Explanation:

Insulators are used to prevent the transfer of heat to areas where it might cause burns or energy loss.