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The equivalent resistance of two resisto...

The equivalent resistance of two resistor connected in series is `6 Omega` and their equivalent resistance is `(4)/(3)Omega`. What are the values of resistances ?

A

`4 Omega, 6 Omega`

B

`8 Omega, 1 Omega`

C

`4 Omega, 2 Omega`

D

`6 Omega, 2 Omega`

Text Solution

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The correct Answer is:
To solve the problem of finding the values of two resistors connected in series and parallel, we can follow these steps: ### Step 1: Set up the equations based on the given information Let the two resistors be \( R_1 \) and \( R_2 \). From the problem, we know: 1. When connected in series, the equivalent resistance is given by: \[ R_1 + R_2 = 6 \, \Omega \quad \text{(Equation 1)} \] 2. When connected in parallel, the equivalent resistance is given by: \[ \frac{R_1 R_2}{R_1 + R_2} = \frac{4}{3} \, \Omega \quad \text{(Equation 2)} \] ### Step 2: Substitute Equation 1 into Equation 2 From Equation 1, we can express \( R_1 + R_2 \) as 6: \[ \frac{R_1 R_2}{6} = \frac{4}{3} \] Now, we can cross-multiply to eliminate the fraction: \[ R_1 R_2 = 6 \cdot \frac{4}{3} \] Calculating the right side: \[ R_1 R_2 = 8 \, \Omega \quad \text{(Equation 3)} \] ### Step 3: Solve the system of equations Now we have two equations: 1. \( R_1 + R_2 = 6 \) (Equation 1) 2. \( R_1 R_2 = 8 \) (Equation 3) We can express \( R_2 \) in terms of \( R_1 \) from Equation 1: \[ R_2 = 6 - R_1 \] Substituting this into Equation 3: \[ R_1 (6 - R_1) = 8 \] Expanding this gives: \[ 6R_1 - R_1^2 = 8 \] Rearranging it into standard quadratic form: \[ R_1^2 - 6R_1 + 8 = 0 \] ### Step 4: Factor the quadratic equation Now we can factor the quadratic equation: \[ (R_1 - 2)(R_1 - 4) = 0 \] This gives us the solutions: \[ R_1 = 2 \, \Omega \quad \text{or} \quad R_1 = 4 \, \Omega \] ### Step 5: Find the corresponding values of \( R_2 \) Using \( R_1 + R_2 = 6 \): - If \( R_1 = 2 \, \Omega \): \[ R_2 = 6 - 2 = 4 \, \Omega \] - If \( R_1 = 4 \, \Omega \): \[ R_2 = 6 - 4 = 2 \, \Omega \] Thus, the values of the resistors are: \[ R_1 = 2 \, \Omega \quad \text{and} \quad R_2 = 4 \, \Omega \] ### Final Answer The values of the resistances are \( 2 \, \Omega \) and \( 4 \, \Omega \). ---
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Knowledge Check

  • The equivalent resistance of two resistors connected in series 6Omega and their parallel equivalent resistance is 4/3Omega . What are the value of resistance?

    A
    `4Omega, 6Omega`
    B
    `8Omega, 1Omega`
    C
    `4Omega, 2Omega`
    D
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  • The equivalent resistance of resistors connected in series is always

    A
    Equal to the mean of component resistors
    B
    Less than the lowest of component resistors
    C
    In between the lowest and the highest of component resistors
    D
    Equal to sum of component resistors
  • The equivalent resistance of three equal resistances connected in series is 27 Omega . There equivalent resistance when connected in parallel is

    A
    `54 Omega`
    B
    `270 Omega`
    C
    `3 Omega`
    D
    `9 Omega`
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