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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Magnetic Field due to a Current

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Magnetic Field due to a Current

Each battery shown in the figure has an emf equal to 5 V ....

Each battery shown in the figure has an emf equal to 5 V5\text{ V}. Determine the magnetic field BB at the point PP for any set of values of the resistances.
Each battery shown in the figure has an emf equal to 5 V . Determine the magnetic field B at the point P for any set of

Options

  1. AA non-zero constant independent of the resistances
  2. BDepends on the values of the resistances
  3. CCannot be determined without knowing the distance of point PP
  4. D00

Correct answer

D. 00

Step-by-step solution

Let the potential at the bottom-middle junction be 0 V0\text{ V} and at the top-middle junction be VV.

From the polarities of the batteries, the potential at the bottom-left node is 5 V5\text{ V} and at the bottom-right node is 5 V5\text{ V}.

Similarly, the potential at the top-left node is V+5 VV + 5\text{ V} and at the top-right node is V+5 VV + 5\text{ V}.

The potential difference across the left resistor is (V+5)−5=V(V + 5) - 5 = V.

The potential difference across the middle resistor is V−0=VV - 0 = V.

The potential difference across the right resistor is (V+5)−5=V(V + 5) - 5 = V.

Applying Kirchhoff's Current Law at the top nodes, the total current leaving through the resistors must be zero:

VR1+VR2+VR3=0\dfrac{V}{R_1} + \dfrac{V}{R_2} + \dfrac{V}{R_3} = 0

V(1R1+1R2+1R3)=0V \left( \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3} \right) = 0

Since the resistances are positive, V=0V = 0.

As the potential difference across each resistor is zero, no current flows in any branch of the circuit.

Since the current is zero everywhere, the magnetic field BB produced by the circuit at point PP is 00.

Answer: 00
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