The voltmeter and ammeter included in the electrical circuit show 9V and 3A, respectively.

| January 11, 2021 | education

The voltmeter and ammeter included in the electrical circuit show 9V and 3A, respectively. The load resistance is 5 times the internal resistance of the current source. What is the resistance of the external circuit?

U = 9 V.
I = 3 A.
Rv = 5 * r.
Rв -?
1.Write Ohm’s law for a closed circuit: I = U / (Rv + r), where U is the voltage that the voltmeter shows, I is the current that the ammeter shows, Rv is the external resistance, r is the internal resistance of the current source.
Since Rв = 5 * r by condition, the formula will take the form:: I = U / (5 * r + r).
I = U / 6 * r.
r = U / 6 * I.
Let us express the external resistance of the circuit: Rv = 5 * r = 5 * U / 6 * I.
Rv = 5 * 9 V * 6 * 3 A = 2.5 ohms.
Answer: the external resistance of the circuit is Rv = 2.5 ohms.



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