Answer:
I = 0.25 A
Explanation:
Resistors
The resistors are the circuit elements that oppose the flow of the current. The more resistance an element has, the less current is allowed to go through it. For a resistor of resistance R to which a voltage V is applied, the equation for the current is given by the Ohm's law:
[tex]\displaystyle I=\frac{V}{R}[/tex]
The power dissipated by a resistor R is given by the Joule's law
[tex]P=I^2R[/tex]
Replacing the first equation into the second, we have
[tex]\displaystyle P=\frac{V^2}{R}[/tex]
The question refers to a resistor that dissipates P=0.5 W when 4 Volts are applied to it, thus we can compute R solving the above equation for R
[tex]\displaystyle R=\frac{V^2}{P}=\frac{4^2}{0.5}=32\Omega[/tex]
If the voltage is changed such that the new power dissipated by the resistor is 2 W, we can compute the new current, solving the equation of Joule's law for I
[tex]\displaystyle I=\sqrt{\frac{P}{R}}=\sqrt{\frac{2}{32}}=0.25\ A[/tex]
