Question

a circuit has a current of 1.2 a. if the voltage decreases to one - third of its original amount while the resistance remains constant, what will be the resulting current? 0.3 a 0.4 a 1.2 a 3.6 a

Explanation:

Step1: Use Ohm's Law

Ohm's Law is \(I = \frac{V}{R}\). Let the original voltage be \(V_1\) and current \(I_1=1.2\space A\), so \(I_1=\frac{V_1}{R}\).

Step2: Analyze the new - voltage case

The new voltage \(V_2=\frac{1}{3}V_1\), and \(R\) is constant. Using Ohm's Law again, \(I_2=\frac{V_2}{R}\). Substitute \(V_2=\frac{1}{3}V_1\) into \(I_2\) formula: \(I_2=\frac{\frac{1}{3}V_1}{R}\).
Since \(I_1 = \frac{V_1}{R}=1.2\space A\), then \(I_2=\frac{1}{3}I_1\).

Step3: Calculate the new current

\(I_2=\frac{1}{3}\times1.2\space A = 0.4\space A\)

Answer:

0.4 A