Find the unknown resistor (R) in circuit 6 V- + 12 V 222 4 Ω 4 Ω I = 2 A + R

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**Finding the Unknown Resistor (R) in a Circuit**

In the given circuit diagram, we have:

- Two voltage sources in series: one with 6 V and another with 12 V, contributing to a total voltage of 18 V across the entire circuit.
- A parallel combination of three resistors:
  - One resistor of 2 ohms (Ω)
  - Two resistors of 4 ohms (Ω) each

The total current flowing through the circuit is given as \( I = 2 \, \text{A} \).

**Steps to Find the Unknown Resistor (R):**

1. **Find the Total Resistance of the Parallel Section:**
   - The parallel resistors are:
     - 2 Ω and two 4 Ω in parallel.
   - The formula to find the total resistance \( R_p \) in parallel is:
     \[
     \frac{1}{R_p} = \frac{1}{2} + \frac{1}{4} + \frac{1}{4} 
     \]
   - This simplifies to:
     \[
     \frac{1}{R_p} = \frac{1}{2} + \frac{1}{2} = 1
     \]
   - Thus, \( R_p = 1 \, \Omega \).

2. **Calculate the Total Resistance in the Circuit:**
   - With \( R_p = 1 \, \Omega \), and assuming the unknown resistor \( R \) is in series with \( R_p \), the equation becomes:
     \[
     R_\text{total} = R_p + R = 1 + R
     \]

3. **Determine the Unknown Resistor (R):**
   - Using Ohm's law, \( V = I \times R \), the total voltage is 18 V and the total current is 2 A, so:
     \[
     18 = 2 \times (1 + R)
     \]
   - Solving for \( R \):
     \[
     18 = 2 + 2R \quad \Rightarrow \quad 16 = 2R \quad \Rightarrow \quad R = 8 \, \Omega
     \]

**Conclusion:**

The unknown resistor \( R \) in the circuit is 8 ohms.
Transcribed Image Text:**Finding the Unknown Resistor (R) in a Circuit** In the given circuit diagram, we have: - Two voltage sources in series: one with 6 V and another with 12 V, contributing to a total voltage of 18 V across the entire circuit. - A parallel combination of three resistors: - One resistor of 2 ohms (Ω) - Two resistors of 4 ohms (Ω) each The total current flowing through the circuit is given as \( I = 2 \, \text{A} \). **Steps to Find the Unknown Resistor (R):** 1. **Find the Total Resistance of the Parallel Section:** - The parallel resistors are: - 2 Ω and two 4 Ω in parallel. - The formula to find the total resistance \( R_p \) in parallel is: \[ \frac{1}{R_p} = \frac{1}{2} + \frac{1}{4} + \frac{1}{4} \] - This simplifies to: \[ \frac{1}{R_p} = \frac{1}{2} + \frac{1}{2} = 1 \] - Thus, \( R_p = 1 \, \Omega \). 2. **Calculate the Total Resistance in the Circuit:** - With \( R_p = 1 \, \Omega \), and assuming the unknown resistor \( R \) is in series with \( R_p \), the equation becomes: \[ R_\text{total} = R_p + R = 1 + R \] 3. **Determine the Unknown Resistor (R):** - Using Ohm's law, \( V = I \times R \), the total voltage is 18 V and the total current is 2 A, so: \[ 18 = 2 \times (1 + R) \] - Solving for \( R \): \[ 18 = 2 + 2R \quad \Rightarrow \quad 16 = 2R \quad \Rightarrow \quad R = 8 \, \Omega \] **Conclusion:** The unknown resistor \( R \) in the circuit is 8 ohms.
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