The voltage across a resistor is found to be given by v _R (t) = (10 V) cos[(120 s⁻¹)t]: 
a) At what frequency does the AC course operate? 
b) If the resistance is 12 Ω, what is the maximum current in this circuit? 
c) What is the RMS voltage of the AC source?

To find the frequency of the AC source, identify the angular frequency \( \omega \) from the given voltage equation \( v_R(t) = (10 \, \text{V}) \cos[(120 \, \text{s}^{-1})t] \). Here, \( \omega = 120 \, \text{s}^{-1} \). The relationship between angular frequency and frequency is \( \omega = 2\pi f \). Solve for \( f \) using \( f = \frac{\omega}{2\pi} \).