The current source produces a voltage of 220 V, its internal resistance is 1 Ohm

The current source produces a voltage of 220 V, its internal resistance is 1 Ohm. Determine what resistance you need to connect to this source so that there is exactly 210 V at its terminals.

The current source produces a voltage (EMF) E = 220 V, its internal resistance r = 1 Ohm; according to Ohm’s law for a complete circuit, the current I in it will be:

I = E / (R + r) or E = I ∙ (R + r);

E = U + I ∙ r, where U is the voltage at the terminals when the load is connected with resistance R, since from Ohm’s law for a section of the circuit, the voltage is U = I ∙ R. We get:

I = (E – U): r

To determine what resistance R needs to be connected to this source so that the voltage at its terminals is U = 210 V, we use Ohm’s law for a section of the circuit:

R = U / I or R = U / ((E – U): r);

R = U ∙ r / (E – U).

Substitute the values ​​of the quantities into the calculation formula:

R = 210 V ∙ 1 Ohm / (220 V – 210 V);

R = 21 ohms.

Answer: a 21 Ohm resistance must be connected to this source.