A tester was connected to the terminals of the coin battery. When this device worked as a voltmeter

| March 13, 2021 | education

A tester was connected to the terminals of the coin battery. When this device worked as a voltmeter with infinite resistance, it showed a voltage of 4.4 V. In the ammeter mode with a resistance of 0.3 ohms, the tester showed a current of 2 A. Determine the internal resistance of the battery.

Let us find the voltage drop across the ammeter, turned on in the voltmeter mode, if a current of 2 A flows through it, and the resistance of the ammeter is 0.3 Ohm:
U = I * R = 2 * 0.3 = 0.6 B.
Let’s find the voltage drop across the internal resistance of the battery, if the battery voltage was 4.4 V without load:
4.4 – 0.6 = 3.8 V.
Let’s find the internal resistance of the battery:
r = U / I = 3.8 / 2 = 1.9 ohms.
The internal resistance of the battery was 1.9 ohms.



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