One ampere is equal to ________.
- A.one coulomb per second
- B.one volt per second
- C.one joule per coulomb
- D.one second per coulomb of charge
Correct answer
Explanation
The correct answer is A, one coulomb per second. Electric current is the rate of flow of electric charge, written as I = Q/t, so one ampere flows when one coulomb of charge passes through a cross-section of a conductor in one second. One coulomb is the charge carried by about 6.25 × 10^18 electrons, so even a small current means a huge number of moving electrons. The ampere is one of the seven SI base units, and it is named after the French scientist André-Marie Ampère. Current is measured with an ammeter, which is always connected in series in a circuit, and small currents are expressed in milliamperes or microamperes. Option B is wrong because volt per second is not a unit of current; the volt measures potential difference. Option C is wrong because one joule per coulomb is the definition of one volt, the unit of potential difference. Option D is wrong because second per coulomb is the reverse of current and is not used as a unit at all. Exam tip: ampere = coulomb per second, volt = joule per coulomb, ohm = volt per ampere.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Liver cells turn the toxic ammonia released from the breakdown of amino acids into urea through the ornithine cycle, also called the urea cycle.
Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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