What voltage must be applied to the ends of a conductor with a resistance of 20 ohms so that a current of 0.5 A appears in it?

According to Ohm’s law, the current in a conductor will be directly proportional to the voltage at the ends of the conductor and inversely proportional to the resistance of the material from which the conductor is made.
I = U / R, where I is the current in the conductor (I = 0.5 A), U is the voltage at the ends of the conductor (V), R is the resistance of the conductor material (R = 20 Ohm).
Let us express and calculate the voltage at the ends of the conductor:
U = I * R = 0.5 * 20 = 10 V.
Answer: It is necessary to supply voltage equal to 10 V.