Table of contents

31. Alternating Current

Alternating Voltages and Currents

Join thousands of students who trust us to help them ace their exams!Watch the first video

Multiple Choice

An AC source produces an alternating current in a circuit with the function $i\left(t\right)=\left(1.5A\right)\cos\left\lbrack\left(250s^{-1}\right)t\right\rbrack$ . What is the frequency of the source? What is the maximum current in the circuit?

f=39.3 Hz

f=250 Hz

f=393 Hz

f=1570 Hz

Verified step by step guidance

Identify the given function for the alternating current: i(t) = (1.5 A) cos[(250 s^{-1}) t].

Recognize that the function is in the form i(t) = I_0 cos(ωt), where I_0 is the maximum current and ω is the angular frequency.

Determine the maximum current, I_0, from the function. Here, I_0 = 1.5 A.

Identify the angular frequency, ω, from the function. Here, ω = 250 s^{-1}.

Use the relationship between angular frequency and frequency: ω = 2πf, to solve for the frequency, f. Rearrange to find f = ω / (2π).

Master Alternating Voltages and Currents with a bite sized video explanation from Patrick

Problem sets built by lead tutors

Expert video explanations

An AC source produces an alternating current in a circuit with the function i(t)=(1.5A)cos[(250s−1)t]i\left(t\right)=\left(1.5A\right)\cos\left\lbrack\left(250s^{-1}\right)t\right\rbracki(t)=(1.5A)cos[(250s−1)t]. What is the frequency of the source? What is the maximum current in the circuit?