Question

In a parallel circuit, there are 3 resistors, each with a resistance of 9 Ω. If the total current is 4 A, what is the total voltage?
A. 1.3 V
B. 12 V
C. 36 V
D. 108 V

Answer 1

Following Ohm's Law, you can compute voltage using the formula:

$V=IR$

Where:
V=voltage
I = current
R = Total Resistance

The problem is you do not have total resistance, but that can be computed as well. To get the total resistance in a parallel circuit the formula you need would be:

$\frac{1}{R_{T}} = \frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}$
$\frac{1}{R_{T}} = \frac{1}{9}+\frac{1}{9}+\frac{1}{9}$
$\frac{1}{R_{T}} = \frac{3}{9}$
$R_{T}= \frac{9}{3}$
$R_{T}= 3$

Total resistance is 3Ω

Now that you have your total resistance, you can solve for voltage:

$V=IR$
$V=(4)(3)$
$V=12V$

Voltage is then 12V. The answer is then B.