Which one of the following statements is NOT correct ?
- A.An ammeter is always connected in series in the circuit to measure the current
- B.A Voltmeter is always connected in parallel in a circuit to measure the voltage
- C.A voltmeter has a high resistance and an ammeter has a low resistance
- D.A voltmeter has a low resistance and an ammeter has a high resistance
Correct answer
Explanation
The correct answer is D, A voltmeter has a low resistance and an ammeter has a high resistance. This reverses the truth: a voltmeter has a very high resistance and an ammeter a very low one.
An ammeter measures the current flowing through a circuit, so it is placed in series and the whole current passes through it. Its resistance is kept very low so that it hardly changes the current it is measuring. A voltmeter measures the potential difference between two points, so it is joined in parallel across them. Its resistance is kept very high so that it draws almost no current away from the circuit. An ideal ammeter has zero resistance and an ideal voltmeter infinite resistance.
A is correct: an ammeter always goes in series. B is correct: a voltmeter always goes in parallel across the part being measured. C is correct: it states the right resistances, high for the voltmeter and low for the ammeter.
Exam tip: Ammeter, series, low resistance; voltmeter, parallel, high resistance.
Practice Questions
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- B.Martin Luther
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- D.Copernicus
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