Question

Pls say the 5 answer​

Answer 1

Answer

Option c

Area of cross-section of the solenoid

Explanation

The magnetic field of a solenoid is given by ,

$\bf B=\mu_o ni\ \;\; \bigstar$

where ,

• n denotes number of turns per unit length

$\rightarrow \rm n=\dfrac{N}{l}$

• i denotes current inside solenoid
• μ₀ denotes 4π × 10⁻⁷ W / A-m

Nature of the core material : By winding the coil over a soft iron cylinder, called core, the magnetic field can be increased several thousands times.

So , it depends on option a

Since B is inversely proportional to length of the solenoid

$\rightarrow \rm B\ \alpha\ \dfrac{1}{l}$

So , option b is correct

Since Magnetic field depends on number of turns of the solenoid .

$\rightarrow \rm B\ \alpha \; n$

So , option d is correct

Since it doesn't depends on area of cross section of the solenoid

So , option c is incorrect . So , answer is option c .