Using Lenz's Law

Q. A circular wire loop of radius $r$ carries a total charge $Q$ distributed uniformly over its length. A small length $dl$ of the wire is cut off. The electric field at the centre due to the remaining wire is:-

1. $\frac{Qdl}{8{\pi }^2{ϵ}_0{r}^3}$
2. $\frac{Qdl}{8\pi {ϵ}_0{r}^3}$
3. $\frac{Qdl}{4{\pi }^2{ϵ}_0{r}^3}$
4. $\frac{Qdl}{2{\pi }^2{ϵ}_0{r}^3}$

Q. A metallic ring is held horizontally and a magnet is allowed to fall vertically through the ring, then the acceleration of this magnet is

1. Equal to $g$
2. More than $g$
3. Less than $g$
4. Sometimes less and sometimes more than $g$

Q. A coil is rotated with constant angular speed in a uniform magnetic field about an axis that is perpendicular to the field.

$\text{STATEMENT-1}:$ The EMF induced in the coil is maximum at the instant the magnetic flux through the coil is zero.

$\text{STATEMENT-2}:$ The angle between the normal to the coil and magnetic field induction is ${90}^{\circ }$.

1. Both $\text{STATEMENT-1}$ and $\text{STATEMENT-2}$ are $\text{TRUE}$ and $\text{STATEMENT-2}$ is the correct explanation of $\text{STATEMENT-1}$
2. Both $\text{STATEMENT-1}$ and $\text{STATEMENT-2}$ are $\text{TRUE}$ but $\text{STATEMENT-2}$ is the $\text{NOT}$ the correct explanation of $\text{STATEMENT-1}$
3. $\text{STATEMENT-1}$ is $\text{FALSE}$ and $\text{STATEMENT-2}$ is $\text{TRUE}$
4. Both $\text{STATEMENT-1}$ and $\text{STATEMENT-2}$ are $\text{WRONG}$

Q. Magnetic field associated with loop is given by graphs below. [Take anticlockwise current positive]

1. 
2. 
3. 
4. 

Q. BAR magnet is moving along the axis of a loop & towards it as shown in the figure.

1. $V_A-V_B$ is negative
2. $V_A-V_B$ is zero
3. $V_A-V_B$ is positive
4. No current in the loop

Q. A loop (circuit) is placed in uniform $\overrightarrow{B}$ and flux through the loop is given by $\varphi =4t$. Find the power supplied to the $6\text{V}$ battery.

1. 6 Watt
2. 2 Watt
3. 3 Watt
4. 5 Watt

Q. A triangle is made of conducting rods. The triangle is released from rest in a vertical plane. If the triangle enters completely into the magnetic field in time t, then the possible answer of t is

1. t = 1 s
2. t = 0.3 s
3. t = 1.7 s
4. t = 0.8 s