The amount of air breathed in and out during a normal respiration by human lungs is referred to as
- A.Vital capacity
- B.Tidal volume
- C.Inspiratory volume
- D.Total lung capacity
Correct answer
Explanation
The correct answer is B, Tidal volume. Tidal volume is the volume of air breathed in or out in one normal, quiet breath, about 500 mL in a healthy adult.
Lung volumes are measured with a spirometer. Beyond the tidal volume, a person can forcibly breathe in about 2,500 to 3,000 mL more (inspiratory reserve volume) and breathe out about 1,000 to 1,100 mL more (expiratory reserve volume). Some air, about 1,100 to 1,200 mL, always stays in the lungs even after the strongest exhalation; this is the residual volume. At about 12 to 16 breaths a minute, a resting adult moves roughly 6 to 8 litres of air a minute.
A is wrong because vital capacity is the most air a person can breathe out after the deepest breath in, about 3,500 to 4,600 mL. C is wrong because inspiratory volume refers to the extra air drawn in by a forced breath, not a normal breath. D is wrong because total lung capacity is all the air the lungs hold after the deepest breath, including the residual volume.
Exam tip: tidal volume about 500 mL; vital capacity = tidal + inspiratory reserve + expiratory reserve; total lung capacity = vital capacity + residual volume.
Practice Questions
View allWhich one of the following statements about sound is NOT correct?
- A.Sound travels at a speed slower than the speed of light
- B.Sound waves are transverse waves
- C.Sound waves are longitudinal waves
- D.Sound travels faster in moist air than in dry air
Show answer
This statement is false, because sound in air travels as longitudinal waves, not transverse waves. In a longitudinal wave, the particles of the medium vibrate back and forth along the direction in which the wave moves, forming compressions and rarefactions.
Read the full explanation →Power of a lens of focal length 25 cm is
- A.+2.5 Dioptre
- B.+3 Dioptre
- C.+4 Dioptre
- D.+5 Dioptre
Show answer
Power is the reciprocal of the focal length in metres, so P = 1 ÷ 0.25 m = +4 D. The power of a lens tells how strongly it converges or diverges light.
Read the full explanation →In which one of the following devices, the light energy is converted into the electrical energy?
- A.Light-emitting diode
- B.Laser diode
- C.Solar cell
- D.Transistor
Show answer
A solar cell turns the energy of sunlight directly into electricity through the photovoltaic effect. A solar cell is a large p-n junction, usually made of silicon.
Read the full explanation →Two conducting wires of the same material and of equal lengths and equal diameters are first connected in parallel and then in series in a circuit across the same potential difference. The ratio of heat produced in parallel and series combinations is
- A.2:1
- B.4:1
- C.1:2
- D.1:4
Show answer
With the same voltage, heat varies inversely as resistance, and the parallel resistance is one-fourth of the series resistance. The two wires are identical, so each has the same resistance R. In series the total resistance is R + R = 2R; in parallel it is R/2.
Read the full explanation →Cornea in human eye
- A.is a light sensitive screen.
- B.is a muscular diaphragm.
- C.contains blood vessels.
- D.is composed of proteins and cells.
Show answer
The cornea is a clear layer made of cells and proteins, chiefly collagen fibres laid out in a regular pattern that keeps it transparent.
Read the full explanation →