The instrument used for detecting the presence of electric current in a circuit is
- A.Refractometer
- B.Galvanometer
- C.Viscometer
- D.Diffractometer
Correct answer
Explanation
The correct answer is B, Galvanometer. A galvanometer detects whether a small electric current is flowing in a circuit and shows its direction.
A moving-coil galvanometer has a coil placed between the poles of a magnet. When current passes through the coil, it experiences a torque and turns, moving a pointer across a scale whose zero is in the middle, so the needle swings one way or the other with the direction of current. It is very sensitive and is used, for example, in the Wheatstone bridge to find the balance point. A galvanometer can be turned into an ammeter by joining a low resistance (shunt) in parallel with it, and into a voltmeter by joining a high resistance in series. It is named after Luigi Galvani.
A is wrong because a refractometer measures the refractive index of a substance. C is wrong because a viscometer measures the viscosity of liquids. D is wrong because a diffractometer studies the structure of materials from the diffraction of X-rays or other waves.
Exam tip: Galvanometer detects current; with a shunt it becomes an ammeter, with high series resistance a voltmeter.
Practice Questions
View allReverberation is a phenomenon associated with a
- A.multiple refraction of sound.
- B.multiple reflection of sound.
- C.single refraction of sound.
- D.single reflection of sound.
Show answer
Reverberation is the persistence of sound in a hall after the source has stopped, caused by repeated reflections from the walls, ceiling and floor.
Read the full explanation →Which one of the following is NOT a basic property of electric charge ?
- A.Charges can be added
- B.Charge is conserved
- C.Charge on a body is always an integral multiple of an electron or a proton charge
- D.Charges can be created and destroyed in an isolated system
Show answer
This goes against the conservation of charge: the total charge of an isolated system always stays the same. Electric charge has three basic properties.
Read the full explanation →Which of the following organelles have their own DNA and ribosomes?
- A.Endoplasmic reticulum and Golgi bodies
- B.Mitochondria and Chloroplast
- C.Endoplasmic reticulum and cytoskeleton
- D.Cell wall and nucleolus
Show answer
These two organelles carry their own circular DNA and their own small (70S) ribosomes, so they can make some of their own proteins.
Read the full explanation →Which one of the following statements is NOT correct ?
- A.All proteins are enzymes
- B.Mostly enzymes are proteins
- C.All fats are energy rich compounds
- D.Glucose is a common carbohydrate
Show answer
This statement is false: enzymes are mostly proteins, but most proteins are not enzymes. Proteins do many jobs in the body.
Read the full explanation →Which one of the following types of radiations has the smallest wavelength?
- A.Microwaves
- B.Infra-red
- C.Visible light
- D.X-rays
Show answer
Of the four, X-rays lie farthest towards the short-wavelength, high-energy end of the electromagnetic spectrum. All electromagnetic waves travel at the speed of light in vacuum but differ in wavelength.
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