# Ammeters and Voltmeters : Notes/W.S.-30 ```Ammeters and Voltmeters : Notes/W.S.-30
Ammeters are used to measure the current. Ideally, they should have a
very low resistance. Ammeters are connected in series with a
resistor or cell (battery).
The reading of the ammeter in the circuit shown below is 3.0 A.
Assume that the ammeter resistance is zero, and that the internal
battery resistance is zero.
4.0 ohms
12 V
A
Voltmeters are used to measure the potential difference between two
points in a circuit. Voltmeters are connected in parallel with a
resistor or cell (battery) to measure the potential difference across
the resistor or cell. The resistance of the voltmeter should be very
large.
The reading of the voltmeter in the circuit shown below is 16 V.
Assume that the voltmeter has a very large resistance and that the
internal battery resistance is zero.
16 V
8.0 ohms
V
Problem:
Find the readings for the ammeter and voltmeter in the circuit shown
below. The value each of the resistors is shown.
4.0
10.
24 V
A
Answers: ammeter 2.4 A, voltmeter 16 V.
8.0
V
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