How many volts are supplied to operate an indicator light on a VCR that has a re

Question

How many volts are supplied to operate an indicator light on a VCR that has a resistance of 160 Ohm, given 22.5 mA passes through it? The internal resistance of a flashlight battery increases gradually with age, even though the battery is not used. The emf, however, remains fairly constant at about 1.5 V. Batteries may be tested for age at the time of purchase by connecting an ammeter directly across the terminals of the battery and reading the current. The resistance of the ammeter is so small that the battery is practically short-circuited. The short-circuit current of a fresh flashlight battery (1.50 V emf) is 14.9 A. What is the internal resistance? What is the internal resistance if the short-circuit current is only 5.7 A? The short-circuit current of a 12 V car battery may be as great as 830 A. What is its internal resistance? When switch S in the figure below is open, the voltmeter V of the battery reads 3.80 V. When the switch is closed, the voltmeter reading drops to 3.63 V, and the ammeter A reads 1.20 A. Assume that the two meters are ideal, so they don't affect the circuit. Find the emf of the battery.

Explanation / Answer

a) v=1.5 v
I= 14.9 A
internal resistance, R= v/I = 1.5/14.9 = 0.1007 ohms
b)
V =1.5 V
I = 5.7 A
internal resistance, R= V/I = 1.5 / 5.7 = 0.263 ohms
c)V =12 V
I = 830 A
internal resistance, R= V/I = 12/830 = 0.0145 ohms

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