Question

The magnetic force acting on a straight wire of length l carrying a current I which is placed perpendicular to the uniform magnetic field B is

• A. IlB
• B. \(\frac{I}{Bl}\)
• C. \(\frac{B}{Il}\)
• D. \(I ^2Bl\)

Answer 1

The Correct Option is A

To determine the magnetic force acting on a straight wire, we apply the formula for the magnetic force \( F \) on a current-carrying conductor in a magnetic field. The formula is:

\[ F = I \cdot l \cdot B \cdot \sin(\theta) \]

Where:

• \( F \) is the magnetic force.
• \( I \) is the current flowing through the wire.
• \( l \) is the length of the wire.
• \( B \) is the magnetic field strength.
• \( \theta \) is the angle between the wire and the magnetic field.

In this scenario, since the wire is placed perpendicular to the magnetic field, \( \theta = 90^\circ \), thus \(\sin(90^\circ) = 1\). This simplifies the formula to:

\[ F = I \cdot l \cdot B \]

Thus, the magnetic force acting on the wire is IlB.

Option	Expression
Correct Option	\( IlB \)

The correct answer is IlB, as it matches the magnetic force \( F \) when the angle \( \theta \) is \( 90^\circ \).

Answer 2

The magnetic force \( F \) acting on a straight wire of length \( l \) carrying a current \( I \), placed perpendicular to a uniform magnetic field \( B \), is given by:

\( F = I l B \)

This equation is derived from the Lorentz force law and is valid when the angle between the wire and magnetic field is \( 90^\circ \), i.e., they are perpendicular.

Correct Answer: \( IlB \)