Practice Conduction in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

Heat transfer through direct physical contact between particles, where faster-moving (hotter) particles collide with and pass kinetic energy to slower-moving (cooler) neighbours.

Touch a hot pan — heat flows from the pan to your hand through direct contact.

Showing a random 20 of 50 problems.

Example 1

easy
In the conduction formula Q=kAΔTd, what does d represent?

Example 2

medium
Two rods, copper (k=400) and steel (k=50), have identical size and ΔT. How many times more heat does copper conduct?

Example 3

easy
Why does the handle of a wooden spoon stay cool when stirring hot soup?

Example 4

medium
A glass window has k=0.8 W/(m⋅∘C), area 2 m2, thickness 0.005 m, and ΔT=15°C. Find the conduction heat flow.

Example 5

hard
A composite slab has glass (k=0.8, d=0.005 m) and wood (k=0.15, d=0.020 m) in series. Area 1 m2, ΔTtotal=30°C. Find Q.

Example 6

easy
Which material is the better thermal conductor: aluminum (k=235) or concrete (k=1.7)?

Example 7

medium
Why are house walls often built with a layer of trapped air or foam between bricks?

Example 8

hard
A house loses 3000 W by conduction through walls when ΔT=25°C. Find the loss when ΔT=10°C.

Example 9

medium
A 0.005 m thick steel plate (k=50) of area 1 m2 has 200°C on one side and 20°C on the other. Find Q.

Example 10

easy
A wall conducts heat with Q=kAΔTd. If the temperature difference ΔT doubles, what happens to the heat flow?

Example 11

hard
A double-glazed window has two glass panes (k=0.8, each 0.004 m thick) separated by a 0.012 m air gap (k=0.025). Area 2 m2, ΔT=20°C. Find the total heat flow. Assume layers in series.

Example 12

challenge
A 0.002 m thick copper base (k=400, area 0.01 m2) of a pan must conduct 8000 W. What temperature difference across the base is required?

Example 13

medium
A conducting bar carries 400 W. If its thermal conductivity k is doubled with all else fixed, find the new heat flow.

Example 14

challenge
A composite wall has two layers (each A=1 m2): brick (k=0.6, d=0.1 m) and fiberglass (k=0.04, d=0.05 m). Inside 20°C, outside −5°C. Find Q and the temperature at the brick-fiberglass interface.

Example 15

medium
A pan base (k=200, A=0.02 m2, d=0.005 m) must transfer 4000 W. Find the required ΔT.

Example 16

challenge
A composite wall has two layers in series, each conducting heat. Layer 1 alone would pass 600 W, layer 2 alone 300 W (at the same overall ΔT). Series conductances combine like 1Q=1Q1+1Q2. Find the actual heat flow.

Example 17

hard
Why are heat sinks on CPUs made of aluminum or copper rather than plastic?

Example 18

easy
You touch a metal railing and a wooden bench, both at room temperature. Which feels colder and why?

Example 19

medium
An insulating foam (k=0.04) is 0.05 m thick, 10 m2, with ΔT=25°C. Find Q.

Example 20

easy
Heat conducts through a wall at 200 W. If you double the wall area A, what is the new heat flow rate?
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