An ammeter and a voltmeter are to be connected in a circuit. Which of the following statements are correct?
(A) Ammeter has negligible resistance.
(B) Ammeter is always connected in series in the circuit.
(C) Voltmeter should have negligible resistance.
(D) Voltmeter should be connected in parallel so that the whole current may pass through it.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (B) only
A meter must measure a quantity without disturbing the circuit. An ammeter carries the circuit current, so it must add almost no resistance; a voltmeter is connected across two points, so it must draw almost no current.
(A) Ammeter has negligible resistance. — Correct. An ammeter is a galvanometer with a low-resistance shunt, so it hardly changes the current it measures.
(B) Ammeter is always connected in series in the circuit. — Correct. The whole current to be measured must pass through it.
(C) Voltmeter should have negligible resistance. — Incorrect. A voltmeter has a very high resistance (a large resistance in series with the galvanometer); a low resistance across a component would take most of its current.
(D) Voltmeter should be connected in parallel so that the whole current may pass through it. — Incorrect. It is connected in parallel, but so that almost no current passes through it, not the whole current.
NCERT (2026-27):
The Moving Coil Galvanometer – “… (ii) For measuring currents, the galvanometer has to be connected in series, and as it has a large resistance, this will change the value of the current in the circuit. To overcome these difficulties, one attaches a small resistance rs, called shunt resistance, in parallel with the galvanometer coil; so that most of the current passes through the shunt.”
The Moving Coil Galvanometer – “… The galvanometer can also be used as a voltmeter to measure the voltage across a given section of the circuit. For this it must be connected in parallel with that section of the circuit. Further, it must draw a very small current, otherwise the voltage measurement will disturb the original set up by an amount which is very large.”