Body Temperature, Energy and Heat Loss MCQs

Radiation and convection are not involved. Latent heat of fusion refers to the heat required to melt a solid, and latent heat of vaporisation refers to the heat that leaves the body with the evaporated sweat.

Author: rikazzz Comment

Body Temperature, Energy and Heat Loss

What causes the cooling effect that we experience when sweating?

The emission of infrared radiation

Conduction of heat to the surrounding air and then convection

Dripping off of warm sweat from our skin

Evaporating water molecules taking their kinetic energy with them

Evaporating water molecules take with them more kinetic energy than the average amount. This decreases the average kinetic energy of the remaining water molecules, hence leaving them at a lower temperature.

Author: rikazzz Comment

Body Temperature, Energy and Heat Loss

Which explanation of the cooling effect produced by an ice pack when applied to the skin is the best one?

Cold applied to the skin causes vasodilation thus allowing more blood to pass through the tissue adjacent to the ice pack and be cooled.

Heat withdrawn from the body is used to provide the ice with the latent heat of vaporisation it requires to melt; until melting is complete, the temperature of the ice pack remains constant.

Cold transfers along its temperature gradient – from ice pack to skin – the melting ice and water mixture ensures good contact with the skin.

Heat withdrawn from the body (at 37 °C) is used to provide the ice (at 0 °C) with the latent heat of fusion it requires to melt; until melting is complete, the temperature of the ice pack doesn’t rise appreciably.

Cold cause vasoconstriction no vasodilation. Body heat provides the ice pack with latent heat of fusion (melting) not vaporisation. Heat transfers, not “cold”.

Author: rikazzz Comment

Body Temperature, Energy and Heat Loss

The thermodynamic temperature scale has an “absolute zero” at −273 °C. In what sense is the zero absolute?

It is 0 Kelvin.

It is exactly 0.00000000….

Particle motion has ceased at this temperature.

It is impossible to reach this temperature.

As temperature is a measure of the kinetic energy of particles, when all particle motion has stopped, temperature is at its lowest point and cannot decrease further.

Author: rikazzz Comment

Body Temperature, Energy and Heat Loss

Why does an ice pack applied to a bruise reduce swelling?

Less fluid leaks from the bruise due to the diminished nerve impulses.

It causes vasoconstriction.

It reduces the metabolic rate at the local site.

It increases the viscosity of blood below the ice pack.

If blood vessels constrict, less blood can flow out of them. Choices C and D are true statements but are beside the point.

Author: rikazzz Comment

Body Temperature, Energy and Heat Loss

A ball initially with 20 J of potential energy has rolled halfway down a slope and is still moving. Which of the following values of kinetic energy (KE) and gravitational potential energy (PE) is it likely to have?

0 J of KE and 0 J of PE

0 J of KE and 10 J of PE

10 J of KE and 10 J of PE

10 J of KE and 0 J of PE

The total amount of PE + KE must still be 20 J. As the ball has rolled halfway down the slope, half of its gravitational potential energy has been transformed into kinetic energy.

Author: rikazzz Comment

Body Temperature, Energy and Heat Loss

Why will the metal bell of a stethoscope that is at the room’s air temperature produce the sensation of cold when placed on the patient’s skin?

The skin is at a lower temperature than the bell.

The stethoscope bell is a good conductor of heat.

The stethoscope bell is a poor conductor of heat.

Sweat evaporating from under the bell cools the skin.

Being a good conductor of heat, the metal bell will gain heat from the skin until all its mass reaches skin temperature. A non-conductor would only gain heat until the surface in contact reached skin temperature.

Author: rikazzz Comment