Question:

An electron is moving along positive x direction in xy plane, magnetic field points in negative z direction, then the force due to magnetic field on electron points in the direction 

Updated On: Mar 20, 2025
  • j

  • -j

  • k

  • -k

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The Correct Option is B

Solution and Explanation

The power dissipated across a resistor is given by the formula: \[ P = \frac{V^2}{R}, \] where \( P \) is the power, \( V \) is the potential difference, and \( R \) is the resistance. If the potential difference \( V \) is doubled, the new potential difference is \( 2V \). The new power \( P' \) is: \[ P' = \frac{(2V)^2}{R} = \frac{4V^2}{R} = 4P. \] Thus, the power dissipated becomes four times when the potential difference is doubled. Hence, the correct answer is \( \boxed{(2)} \).
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Concepts Used:

Biot Savart Law

Biot-Savart’s law is an equation that gives the magnetic field produced due to a current-carrying segment. This segment is taken as a vector quantity known as the current element. In other words, Biot-Savart Law states that if a current carrying conductor of length dl produces a magnetic field dB, the force on another similar current-carrying conductor depends upon the size, orientation and length of the first current carrying element. 

The equation of Biot-Savart law is given by,

\(dB = \frac{\mu_0}{4\pi} \frac{Idl sin \theta}{r^2}\)

Application of Biot Savart law

  • Biot Savart law is used to evaluate magnetic response at the molecular or atomic level.
  • It is used to assess the velocity in aerodynamic theory induced by the vortex line.

Importance of Biot-Savart Law

  • Biot-Savart Law is exactly similar to Coulomb's law in electrostatics.
  • Biot-Savart Law is relevant for very small conductors to carry current,
  • For symmetrical current distribution, Biot-Savart Law is applicable.

For detailed derivation on Biot Savart Law, read more