Fix remaining V / U voltage symbols inconsistency

problemexpres.tex

@@ -11,10 +11,10 @@ Electrical Power, in a circuit is the amount of energy that is absorbed or produ
 \subsection{Ohm's law}
 Ohm's Law deals with the relationship between voltage and current in an ideal conductor. This relationship states that: The potential difference (voltage) across an ideal conductor is proportional to the current through it \cite{henry2008ohm}. The constant of proportionality is called the \textit{resistance}.
 $$I = \frac U R $$
-where I is the current expressed in Amperes [A], V is the voltage, bearing the Volt units [V] and R is the electrical resistance in ohms [$\Omega$].
+where I is the current expressed in Amperes [A], U is the voltage, bearing the Volt units [V] and R is the electrical resistance in ohms [$\Omega$].
 
 The Ohms's law can be further expanded \cite{beaty1998electric}, to get these three quantities in relationship with \textbf{power}, such as
-$$P = I \cdot V = I^2 \cdot R = \frac{U^2}R$$
+$$P = I \cdot U = I^2 \cdot R = \frac{U^2}R$$
 
 \subsection{Direct current (DC) circuits}
 Generally, Ohm's law is used on \gls{dc} circuits. A DC voltage or current has a fixed magnitude (amplitude) and a definite direction associated with it. Both DC currents and voltages are produced by power supplies, batteries, dynamos and solar cells to name a few.