Question

BX and BY are the magnetic field at the centre of two coils X and Y, respectively each carrying equal current. If coil X has 200 turns and 20 cm radius and coil Y has 400 turns and 20 cm radius, the ratio of BX and BY is

• A. 1:1
• B. 1:2
• C. 2:1
• D. 4:1

Answer 1

Answer: (B)

1:2

Answer 2

$B=\frac {μ_0NI}{2R}$

$\frac {B_x}{B_y}=\frac {N_xR_y}{N_yR_x}$

$\frac {B_x}{B_y}=\frac {200×20}{400×20}$

$\frac {B_x}{B_y}=\frac 12$

So, the correct option is (B): $1:2$