The device used for measuring electric current in a circuit is called
- A.Ammeter
- B.Motor
- C.Voltmeter
- D.Generator
Correct answer
Explanation
The correct answer is A, Ammeter. An ammeter measures the electric current flowing in a circuit, in amperes.
An ammeter is always connected in series with the part of the circuit whose current is to be measured, so that the whole current passes through it. For this reason it has a very low resistance, and an ideal ammeter has zero resistance, so that it does not change the current it measures. A galvanometer, which detects small currents, can be turned into an ammeter by connecting a low resistance (a shunt) in parallel with it.
B is wrong: an electric motor converts electrical energy into mechanical energy; it does not measure anything.
C is wrong: a voltmeter measures potential difference in volts; it is connected in parallel and has a very high resistance.
D is wrong: a generator converts mechanical energy into electrical energy.
Exam tip: ammeter = current, in series, low resistance; voltmeter = potential difference, in parallel, high resistance; galvanometer + shunt = ammeter.
Practice Questions
View allThe principle involved in paper chromatography is
- A.Absorption
- B.Partition
- C.Solubility
- D.Volatility
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Paper chromatography separates substances because each one divides, or partitions, itself differently between two liquid phases. In paper chromatography the stationary phase is the water held in the cellulose fibres of the paper, and the mobile phase is the solvent that rises up the paper by capillary action.
Read the full explanation →Which one of the following phenomena CANNOT be exhibited by sound waves ?
- A.Reflection
- B.Refraction
- C.Interference
- D.Polarisation
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Sound in air is a longitudinal wave, and only transverse waves can be polarised. Polarisation means restricting the vibrations of a wave to a single plane.
Read the full explanation →Which one of the following is NOT a luminous object ?
- A.Sun
- B.Electric lamp
- C.Candle
- D.Moon
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Read the full explanation →In experiment #1, a bar magnet is moved towards a conducting wire loop axially, with the magnet's north pole facing the loop. In experiment #2, the same process as in experiment #1 is repeated except that the south pole of the magnet faces the loop. Which one of the following statements is true in this context?
- A.The direction of current in the loop will be of opposite nature in both the experiments.
- B.The direction of current in the loop will be the same in both the experiments.
- C.No current will flow in either of the two experiments.
- D.More current will flow in the loop in experiment #1.
Show answer
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Read the full explanation →Which one of the following statements about classification of plants is correct?
- A.Thallophytes have well differentiated body design
- B.Funaria is a fungus
- C.All Pteridophytes are Phanerogams
- D.Vascular system is not found among Bryophytes
Show answer
Mosses and liverworts have no xylem or phloem, so water moves through them cell to cell. Bryophytes, such as Funaria (a moss) and Marchantia (a liverwort), are called the amphibians of the plant kingdom because they live on land but need water for fertilisation.
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