The short-circuit current is equal to Isc = 7.5 A which is equal to the voltage across

| September 25, 2021 | education

The short-circuit current is equal to Isc = 7.5 A which is equal to the voltage across the external resistance R = 4 ohms if the emf of the source is 6 V.

Isc = 7.5 A.
R = 4 ohms.
EMF = 6 V.
U -?
The voltage across the external resistance will be determined by Ohm’s law for the section of the circuit: I = U / R.
Where U is the voltage across the resistance R.
U = I * R.
Let’s write Ohm’s law for a closed circuit: I = EMF / (r + R). Where I is the current in the circuit, EMF is the current source, r is the resistance of the current source, R is the external resistance.
In case of a short circuit, the external resistance R = 0, therefore Isc. = EMF / r.
r = EMF / Isc.
I = EMF / (EMF / Isc + R).
U = EMF * R / (EMF / Isc + R).
U = 6 V * 4 ohms / (6 V / 7.5 A + 4 ohms) = 5 V.
Answer: the voltage across the resistance R = 4 ohms, the voltage will be U = 5 V.



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