Question

A uniform magnetic field of $1.5T$ exists in a cylindrical region of radius $10.0cm$, it's direction being parallel to the axis along east to west. A current carrying wire in north-south direction passes through this region. The wire intersects the axis and experiences a force of $1.2N$ downwards. If the wire is turned from north-south to northeast-southwest direction, then the magnitude and the direction of the force is

• A. $1.2N$, upwards
• B. $1.2\sqrt{2}N$, downward
• C. $1.2N$, downwards
• D. $\frac{1.2}{\sqrt{2}}N$, downwards

Answer 1

The correct option is C $1.2N$, downwards

Initially: $1.2N=1(\overrightarrow{l}\times \overrightarrow{B})$ downward

In the given condition:

$F=I\frac{l}{sin\theta }Bsin\theta =IlB=1.2N$ downward.