Physics · Science General

Heat Transfer Mechanisms

828 Questions

Heat Transfer Mechanisms deal with the movement of thermal energy through conduction, convection, and radiation. It involves practical applications like ocean heat storage and atmospheric heating. These fundamental physics concepts are frequently asked in general science sections.

Thermal conductionHeat convectionThermal radiationSpecific heatStates of matter

Heat Transfer Mechanisms Questions

Multiple choice physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

The temperature of water at the bottom of a large waterfall is generally higher than that of the water at the top, because

  1. the falling water absorbs heat from the sun

  2. the KE of the falling water is converted into heat

  3. the water at the bottom has greater PE

  4. rocks on the bed of the river give out heat
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Water is slightly warmer at the bottom of a waterfall than at the top because the gravitational potential energy is converted first to kinetic energy of the falling water, and finally to heat energy as it comes to rest at the bottom.

Multiple choice physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

The temperature of water at the bottom of a waterfall is higher than that ofthe water at the top, because

  1. falling water absorbs heat from the sun

  2. kinetic energy of the falling water is converted into heat

  3. water at the bottom has greater potential energy

  4. the rocks on the river bed give out heat
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When water falls from top of a waterfall, it has a force of friction being exerted on it due to which some of its kinetic energy gets converted into heat energy.

Thus the temperature of water at the bottom of waterfall is higher than that at the top.

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

A metal plate can be heated by

  1. passing either a direct or alternating current through the plate.

  2. placing in a time varying magnetic field.

  3. placing in a space varying magnetic field, but does not vary with time.

  4. both (a) and (b) are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When a metal plate is getting heated, it may be due to the passage of direct current, alternating current or even induced current through the plate. As time varying magnetic field produces induced current  in the plate, so both (a) and (b) are correct.

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

The temperature of a metal wire rises when an electric current is passed through it because:

  1. collision of conduction electrons with the atoms of metal gives them energy which appears as heat

  2. .when electrons fall from higher energy level to lower energy level, heat energy is released

  3. collisions of metal atoms with each other releases heat energy.

  4. collisions of conduction electrons with each other releases heat energy.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

A metallic conductor has a large number of free electrons in it. When a potential difference is applied across the ends of a metallic wire, the free electrons begin to drift from the low potential to the high potential region. These electrons collide with the positive ions (the atoms which have lost their electrons). In these collisions, energy of the electrons is transferred to the positive ions and they begin to vibrate more violently. As a result, heat is produced. Greater the number of electrons flowing per second, greater will be the rate of collisions and hence more heat is produced.
Hence, the temperature of a metal wire rises when an electric current is passed through it because collision of conduction electrons with the atoms of metal gives them energy which appears as heat.

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

When a current flows through a conductor, its temperature

  1. increases

  2. decreases

  3. remains same

  4. may increase or decrease
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As we know,

$Power=I^2R$
Therefore, this power is released in the form of heat in the conductor and this heat increases the temperature of the conductor.
Hence, temperature increases.

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

The amount of heat produced in a wire depends on its material-

  1. Length

  2. Thickness

  3. Length and thickness

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

Amount of heat produced in wire = $I^2R$

Where $R$ = Resistance of wire
            $I$ = Current through wire
As resistance of wire   $R \propto   \dfrac{L}{A}$
So heat produced depends on Length as well as thickness.        

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

When a current flows through a conductor its temperature

  1. May increase or decrease

  2. Remains same

  3. Decreases

  4. Increases
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

According to Joule's heating effect of current, heat energy is generated across a conductor due to the current flowing through it and hence its temperature increases.

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

Heating effect of current is due to

  1. flow of voltage through the conductor.

  2. flow of current through a conductor.

  3. both A and B.

  4. neither A nor B.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Whenever an electric current is passed through a conductor, it gets heated up. And the amount of heat created is directly proportional to the square of the current.

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

Whenever an electric current is passed through a conductor,it gets heated up.this means that a part of electrical energy, given to the conductor, gets converted to

  1. potential energy

  2. gravitational energy

  3. heat energy

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Whenever an electric current is passed through a conductor,it gets heated up. This indicates that a part of electrical energy gets converted into heat energy.

Multiple choice physics electric current and its effects thermal effect of electric current heating effect of electric current effect of electric current

An electric heater kept in vacuum is heated continuously by passing electric current. Its temperature:

  1. will go on rising with time

  2. will stop after sometime as it will loose heat to the surroundings by conduction

  3. will rise for sometime and thereafter will starts falling

  4. will become constant after sometime because of loss of heat due to radiation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Treating initially that there is no radiation and on applying voltage to the heater, the temperature of the heater rises. As the temperature rises, the radiation also increases.
As the input power($i^2r$) is constant, the output power should also be constant.
Initially temperature will be increasing and  radiation as well. When the heater reaches a certain temperature, the radiation power equals the input power and the temperature of the heater stops rising.
Thus temperature becomes constant after some time.  

Multiple choice physics electric current and circuit thermal effect of electric current heating effect of electric current electric current and its effects

Laws of heating is given by :

  1. Joule

  2. Ohm

  3. Maxwell

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

Answer is A.

The heat which is produced due to the flow of  current   within an electric wire, is expressed in Joules.
James Prescott Joule was an English physicist who studied the nature of heat and established its relationship to mechanical work. He therefore laid the foundation for the theory of conservation of energy, which later influenced the First Law of Thermodynamics. He also formulated the Joules laws which deal with the transfer of energy.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Mircrowave oven acts on the principle of 

  1. Giving rotational energy to water

  2. Giving translational energy to water molecular

  3. Giving vibrational energy to water molecules

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

Microwave oven act on the principle of transferring electron from lower 

to higher energy level in water molecule.