فيزياء الإمارات للصف العاشر و الحادي عشر و الثاني عشر (كتاب Mc Graw ...
A voltmeter is placed in parallel with the portion of the circuit whose difference in potential is to be measured. A voltmeter must have very high resistance for the same reason that an ammeter has low resistance. If the voltmeter had low resistance, it would lower the resistance of the portion of the circuit it is across and increase the current in the circuit.