Question

The graph shows the variation in magnetic flux $\left(\varphi \right)$ with time$\left(t\right)$ through a coil. Which of the following statements given below is not correct?

• A. There is a change in the direction as well as magnitude of the induced emf between $C$ and $E$.
• B. The induced emf is zero at $D$
• C. There is a change in the direction as well as magnitude of induced emf between $A$ and $C$.
• D. The induced emf is zero at $A$.

Answer 1

The correct option is D The induced emf is zero at $A$.

We know that induced emf,

$E=-\frac{d\varphi }{dt}$


For $AB$, $\frac{d\varphi }{dt}=+ve\Rightarrow E_{AB}=-ve$

For $BC$, $\frac{d\varphi }{dt}=-ve\Rightarrow E_{BC}=+ve$

For $CD$, $\frac{d\varphi }{dt}$ varies from negative value to zero $\Rightarrow E_{CD}=+ve$ or $0$.

For $DE$, $\frac{d\varphi }{dt}$ varies from zero to positive value $\Rightarrow E_{DE}=-ve$ or $0$.

At $A$, $\frac{d\varphi }{dt}$ has some positive value thus $E_A=-ve$.

At $D$, $\frac{d\varphi }{dt}=0\Rightarrow E=0$


Hence, $\left(D\right)$ is the correct answer.