Question

A straight wire of mass 100 g and length m carries current of 2A. it is suspended in mid air by applying uniform horizontal magnetic field B perpendicular to wire. the magnitude of B is

• A. 4t
• B. 2T
• C. 1T
• D. 0.5T

Answer 1

The correct option is D 0.5T

$\text{Given}$ : Mass of wire (m) = 100 grams or 0.1 kg

length (L) = 1 m

Current (I) = 2 A

$\text{To find}$: The magnitude of B

$\text{Solution}$:

We know that,

Acceleration due to gravity (g) = 9.8$\frac{m}{s^2}$

Now the weight of the wire will be balanced by the magnetic force acting in the opposite direction.

Let the magnetic field be B. So,

mg = ILB

$\therefore B=\frac{mg}{IL}$

$B=\frac{0.1\times 9.8}{2\times 1}$

$\therefore B=0.49T\sim 0.5T$

$\text{Hence option D is correct.}$