Practice Heat Transfer in Physics

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

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Quick Recap

The spontaneous flow of thermal energy from a hotter object to a cooler one until they reach thermal equilibrium (the same temperature).

Heat always flows from hot to cold on its own — reversing this requires external work.

Showing a random 20 of 50 problems.

Example 1

easy
Name the three methods of heat transfer.

Example 2

easy
A hot cup of coffee is left on a table. Over time, what happens to its temperature and why?

Example 3

medium
A hot 0.5 kg stone (c=800c = 800) cools from 120°C to 40°C in air. How much heat does it give to the air?

Example 4

easy
When does spontaneous heat transfer between two objects stop?

Example 5

medium
Why do thermos bottles have shiny inner surfaces?

Example 6

medium
A 2 kg block at 100°C transfers 50000 J of heat to its surroundings. If c=500c = 500, find its new temperature.

Example 7

medium
A 0.4 kg0.4\text{ kg} copper rod (c=385c=385) cools from 90°C90°C to 25°C25°C. How much heat does it release?

Example 8

easy
A refrigerator moves heat from cold food to a warm room. Why does this not happen spontaneously?

Example 9

medium
Object A (80°C) and object B (20°C) reach equilibrium at 35°C. Did A or B have the larger heat capacity?

Example 10

hard
How long does a 2 kW2\text{ kW} heater take to melt 0.5 kg0.5\text{ kg} of ice already at 0°C0°C? (Lf=334,000 J/kgL_f = 334{,}000\text{ J/kg}.)

Example 11

easy
How much heat is needed to raise 0.2 kg0.2\text{ kg} of water by 25°C25°C? (c=4200c = 4200.)

Example 12

medium
A 0.3 kg0.3\text{ kg} iron block (c=450c=450) at 20°C20°C absorbs 4050 J4050\text{ J} of heat. Find the new temperature.

Example 13

easy
True or false: temperature and heat are the same thing.

Example 14

easy
Identify the primary mode of heat transfer in each case: (a) a metal spoon in hot soup, (b) warmth from a campfire, (c) a pot of water being heated on a stove.

Example 15

hard
2 kg2\text{ kg} of 100°C100°C water is boiled away to steam at 100°C100°C. How much heat is needed? (Lv=2.26×106 J/kgL_v = 2.26\times 10^6\text{ J/kg}.)

Example 16

easy
Identify the mode of heat transfer: heat traveling up a metal frying-pan handle.

Example 17

medium
Why are pots and pans often made of metal but their handles of wood or plastic?

Example 18

medium
0.2 kg0.2\text{ kg} of metal at 80°C80°C is mixed with 0.3 kg0.3\text{ kg} of water (cw=4200c_w=4200) at 20°C20°C. They reach 30°C30°C. Find the metal's specific heat (cmc_m).

Example 19

medium
A thermos flask uses a vacuum between its double walls. Explain why this reduces heat transfer, and which mode(s) of heat transfer it primarily blocks.

Example 20

medium
A warm 1 kg metal (c=400c = 400) cools from 90°C to 30°C in a room. How much heat did it give to the room?
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