Question

The figure shows a conducting loop being pulled out of a uniform magnetic field with a constant speed $v$. Which of the four plots, shown in the figure, may represent the power delivered by the pulling agent as a function of the constant speed $v$.

• A. $\text{A}$
• B. $\text{B}$
• C. $\text{C}$
• D. $\text{D}$

Answer 1

The correct option is B $\text{B}$



According to lenz's law , to oppose the flux decrease , a clockwise current will be induced in the loop.

Motional induced e.m.f. and induced current in the loop is, $E=Bvl$

$\Rightarrow i=\frac{Bvl}{R}$

Magnetic force acting on the loop is, $F_m=\frac{B^2{l}^{2}v}{R}=F_{ext}\text{as}v=\text{constant}$

$F_{ext}=\frac{B^2{l}^{2}v}{R}$
Hence power $=\overrightarrow{F}.\overrightarrow{v}=\frac{B^2{v}^2{l}^2}{R}$


<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(B\right)$ is the correct answer.