Question

What happens to the force between magnetic poles when their pole strength and the distance between them are both doubled

• A. Force increases to two times the previous value
• B. No change
• C. Force decreases to half-the previous value
• D. Force increases to four times the previous value

Answer 1

Answer: (B)

No change

The law states that the force of attraction or repulsion between two magnetic poles is directly proportional to the product of the strengths of the poles and inversely proportional to the square of the distance between them.

Hence the new force $F_2$ will be given by

$\frac{F_2}{F_1}=\frac{\frac{m_{A2}\times m_{B2}}{{d_2}^2}}{\frac{m_{A1}\times m_{B1}}{{d_1}^2}}=\frac{\frac{2m_{A1}\times 2m_{B1}}{{2d_1}^2}}{\frac{m_{A1}\times m_{B1}}{{d_1}^2}}=1$

$\therefore$ $F_2=F_1$