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If R1 = 6 Ω, R2 = 8 Ω, R3 = 2 Ω, ε1 = 4 V, and ε2 = 14 V, what is the current in R2?

Verified Answer :

We need to formulate an equation using Kirchhoff's Law and the 2 equations formed are listed below:
-4i1+10i2=14 and 7i1-8i2=4
Since we have two equations and two unknowns, we can now solve for current 1(i1) and current 2 (i2). Then we have i1=2 amperes and i2=3 amperes.
Therefore, the current in R2 is 1 ampere.

The current in the resistor \(R_2\) is \(\boxed{1\text{ A}}\).


Further Explanation:

There are two rectangular loops in the given circuit.

To obtain the current in both the loops we will apply Kirchhoff’s voltage law.


Given:

The resistance of first resistor is \(6\) Ω.

The resistance of second resistor is \(8\) Ω.

The resistance of third resistor is \(2\) Ω.

The voltage of first cell is \(4\text{ V}\).

The voltage of second cell is \(14\text{ V}\).


Concept:

Kirchhoff’s law in left side loop:

\(i_1R_1+(i_1-i_2)R_2=\epsilon_1\)

Substitute \(6\) Ω for \(R_1\), \(8\) Ω for \(R_2\) and \(4\text{ V}\) for \(\epsilon_1\) in above equation and simplify.

\(7i_1-4i_2=2\)                                                                                  …… (I)


Kirchhoff’s law in right side loop:

\((i_2-i_1)R_2+i_2R_3=\epsilon_2\)

Substitute \(8\) Ω for \(R_2\), \(2\) Ω for \(R_3\) and \(14\text{ V}\) for \(\epsilon_2\) in above equation and simplify.

\(-4i_1+5i_2=7\)                                                                               …… (II)

Multiply equation (I) with \(5\)

\(35i_1-20i_2=10\)                                                                          …… (III)

Multiply equation (II) with \(4\)

\(-16i_1+20i_2=28\)                                                                       …… (IV)


On adding equation (III) and equation (IV), we get

\(i_1=2\text{ A}\)


Substitute \(2\text{ A}\) for \(i_1\) in equation (I) and rearrange for \(i_2\) .

\(i_2=3\text{ A}\)


Current in second resistor:

\(\begin{aligned}I&=|i_1-i_2|\\&=1\text{ A}\end{aligned}\)


Thus, the current in the resistor \(R_2\) is \(\boxed{1\text{ A}}\).


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Answer Details:

Grade: College

Subject: Physics

Chapter: Electricity


Keywords:

R1, R2, R3, E1, E2, current, Kirchhoff’s, voltage, loop, circuit, resistor, 6 ohm, 2 ohm, 8 ohm, 4 volt, 14 volt and law.

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