Tag: heat energy transfers

Quizzes (5) Questions (137)

Questions Related to heat energy transfers

Multiple choice physics heat energy transfers heat energy heat, internal energy and work internal energy

Heat is a from of ______

  1. Energy

  2. Work

  3. Power

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In thermodynamics, heat is a type of energy transfer in which energy flows from a warmer substance or object to a colder one. It can be defined as the total amount of transferred energy excluding any macroscopic work that was done and any transfer of part of the object itself Transfer of energy as heat can occur through direct contact, through a barrier that is impermeable to matter (as in conduction), by radiation between separated bodies, by way of an intermediate fluid (as in convective circulation), or by a combination of these By contrast to work, heat involves the stochastic (random) motion of particles (such as atoms or molecules) that is equally distributed among all degrees of freedom, while work is confined to one or more specific degrees of freedom such as those of the center of mass.

Multiple choice physics heat energy transfers heat energy heat, internal energy and work internal energy

When heat energy is given out by a hot substance then the kinetic energy of its molecules _________. Fill in the blank. 

  1. Increases

  2. Decreases

  3. Remain same

  4. None
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When heat energy is given out by a hot substance, the internal energy of the substance decreases hence kinetic energy of its molecules i.e. they become slower in motion.

Multiple choice physics heat energy transfers heat energy heat, internal energy and work internal energy

Which of the following is false for heat?

  1. It is a form of energy.

  2. It cannot be seen but only can be felt.

  3. If a body's temperature is increased, it gains heat energy.

  4. It is always produced from chemical energy.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Heat is a form of energy. It can only be felt and not seen. 

Heat transferred to a body is given by
$Q=ms\Delta T$
Hence, when temperature of body is increased, it gains heat energy. It flows from hotter body to colder body. Other forms of energy can also convert to heat energy. For example, for a sliding block on a rough surface, most of the kinetic energy is converted into heat energy.

Multiple choice physics heat energy transfers heat energy heat, internal energy and work internal energy

At the molecular level what can be said about Heat energy?

  1. Heat energy is equal to total mechanical energy of all its molecules

  2. Heat energy is equal to total potential energy of all its molecules

  3. Heat energy is equal to total kinetic energy of all its molecules

  4. Heat energy is equal to total heat energy of all its molecules
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

At molecular level, heat energy is equal to mechanical energy of all molecules. Mechanical energy of the molecules is the sum of total Kinetic energy and potential energy of molecules.

Multiple choice physics heat energy transfers heat energy heat, internal energy and work internal energy

Select the option which describes the best definition of heat in the context of thermal energy?

  1. energy possessed by a system due to movement of particles within the system

  2. the measure of thermal energy

  3. thermal energy transferred from one object to another

  4. energy possessed by an object due to the temperature of the object

  5. potential energy
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heat is a thermal energy that is transferred from hotter body to a cooler body.

Multiple choice physics heat energy transfers heat energy heat, internal energy and work internal energy

The temperature inside a refrigerator is $t _2$ $^0C$ and the room temperature is $t _1$ $^0C$. The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be   

  1. $\frac{t _1}{t _1 - t _2}$

  2. $\frac{t _1 + 273}{t _1 - t _2}$

  3. $\frac{t _2 + 273}{t _1 + t _2}$

  4. $\frac{t _1 + t _2}{t _1 + 273}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The coefficient of performance (COP) for a heat pump is defined as Q_h / W. In terms of absolute temperatures (Kelvin), the heat delivered to the room for each unit of work is T_1 / (T_1 - T_2), where T_1 and T_2 are in Kelvin.

Multiple choice physics heat energy transfers heat energy heat, internal energy and work internal energy

How much heat energy is gained when 5kg of water at $20^{ _-^0}C$ I brought to its boiling point? (Specific heat of water = 4.2 kJ $kg^{-1} C^{-1}$) -

  1. 1680 kJ

  2. 1700 kJ

  3. 1720 kJ

  4. 1740 kJ
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The heat energy required is calculated using Q = m * c * delta_T. Here, m = 5 kg, c = 4.2 kJ/kg C, and delta_T = 100 - 20 = 80 C. Thus, Q = 5 * 4.2 * 80 = 1680 kJ.