Angela is an electrical engineer who is testing the voltage of a circuit given a certain current and resistance. She uses the following formula to calculate voltage:

[tex]\[ \text{voltage} = (\text{current}) \times (\text{resistance}) \][/tex]

The circuit she tests has a current of [tex]\(3 + j4\)[/tex] amps and a resistance of [tex]\(4 - j6\)[/tex] ohms.

What is the voltage of the circuit?

A. [tex]\(36 - j2\)[/tex] volts

B. [tex]\(-12 + j34\)[/tex] volts

C. [tex]\(36 + j34\)[/tex] volts

D. [tex]\(-12 - j2\)[/tex] volts



Answer :

To determine the voltage of the circuit, we need to use the given formula:
[tex]\[ \text{voltage} = \text{current} \times \text{resistance} \][/tex]

Given:
- The current is [tex]\( 3 + 4j \)[/tex] amps
- The resistance is [tex]\( 4 - 6j \)[/tex] ohms

Let's denote the current as [tex]\( I = 3 + 4j \)[/tex] and the resistance as [tex]\( R = 4 - 6j \)[/tex].

First, we perform the multiplication of the complex numbers using the distributive property of multiplication over addition for complex numbers:

[tex]\[ (3 + 4j) \times (4 - 6j) \][/tex]

We need to multiply each term in the first complex number by each term in the second complex number:

[tex]\[ (3 \times 4) + (3 \times -6j) + (4j \times 4) + (4j \times -6j) \][/tex]

Calculate each term separately:
- [tex]\( 3 \times 4 = 12 \)[/tex]
- [tex]\( 3 \times -6j = -18j \)[/tex]
- [tex]\( 4j \times 4 = 16j \)[/tex]
- [tex]\( 4j \times -6j = -24j^2 \)[/tex]
- Since [tex]\( j^2 = -1 \)[/tex], [tex]\( -24j^2 = -24(-1) = 24 \)[/tex]

Now combine these results:

[tex]\[ 12 - 18j + 16j + 24 \][/tex]

Simplify by combining like terms:

- The real parts: [tex]\( 12 + 24 = 36 \)[/tex]
- The imaginary parts: [tex]\( -18j + 16j = -2j \)[/tex]

Thus, the voltage is:

[tex]\[ 36 - 2j \][/tex]

Referencing the options provided:
[tex]\[ 36 - 2j \text{ volts} \][/tex]

Therefore, the correct answer is:

[tex]\[ 36 - 2j \text{ volts} \][/tex]

You should choose the option:
[tex]\[ \boxed{36 - j 2 \text{ volts}} \][/tex]