Electromagnetic Induction

What is the physical significance of Lenz's Law?

If a magnetic field is $B$ and the area is $A$, the flux is zero when the angle between them is:

According to Faraday, an emf is induced in a conductor whenever it:

The flux linked with a circuit depends on:

A rectangular coil of $20$ turns and area of cross-section $25\text{ cm}^2$ has a resistance of $100\text{ }\Omega$. If a magnetic field which is perpendicular to the plane of the coil changes at a rate of $1000\text{ Tesla/sec}$, the current in the coil is:

The magnetic flux $\Phi$ linked with a coil is related to the number of turns $N$ and the magnetic field $B$ as $\Phi = NBA \cos \theta$. If the coil is rotated such that $\theta$ changes from $0^\circ$ to $180^\circ$, the change in flux is:

Two coils have a mutual inductance of $0.005\text{ H}$. The current changes in the first coil according to $I = I_0 \sin \omega t$, where $I_0 = 10\text{ A}$ and $\omega = 100\pi\text{ rad/s}$. The maximum value of induced emf in the second coil is:

A conducting rod is pushed with a constant velocity $v$ along two smooth conducting rails that meet at an angle $\theta$ at a vertex $O$. The rod is always perpendicular to the bisector of the angle $\theta$ and maintains electrical contact with the rails. A uniform magnetic field $B$ is directed perpendicular to the plane of the rails. If the rod starts from the vertex $O$ at time $t = 0$, the magnitude of the induced emf in the rod at time $t$ is given by:

A solenoid has an inductance of $10$ H and a resistance of $2$ $\Omega$. It is connected to a $10$ V battery. How long will it take for the magnetic energy to reach $1/4$ of its maximum value?

A coil of wire is being pulled out of a magnetic field. The force required to pull the coil at constant velocity is proportional to:

What is the induced EMF when a wire moves in a direction that is 30 degrees to the magnetic field, compared to when it moves perpendicularly?

If a rod is moved in a magnetic field, the induced current flows only if:

A metallic disc of radius $R$ rotates with angular velocity $\omega$ in a uniform magnetic field $B$ perpendicular to its plane. The EMF induced between the center and the rim is:

The induced EMF is also known as:

A metal rod of length $l$ is rotated with angular velocity $\omega$ about an axis at distance $l/4$ from one end. The potential difference between the ends is:

Two rods of lengths $l_1$ and $l_2$ are rotating with same angular velocity $\omega$ in a uniform magnetic field. The ratio of EMF induced across them is:

A rod of length $L$ and resistance $R$ slides on two frictionless rails. If a constant force $F$ is applied to it, the terminal velocity $v$ attained by the rod in a magnetic field $B$ is:

A rod of length $L$ moves with speed $v$ in a field $B$. A battery of EMF $V_b$ is connected in the circuit such that it opposes the motional EMF. The current in the circuit is zero if $v$ is:

A Faraday disc dynamo has a radius $R$ and rotates at $\omega$ in a uniform field $B$. The power generated when connected to an external load $R_L$ (neglecting disc resistance) is:

A rod of length $L$ is moved at velocity $v$ in a magnetic field $B$. The induced EMF is $V$. If the rod is bent into a semicircle and moved with the same $v$ and $B$ (with diameter perpendicular to $v$), the new EMF is:

A coil has a self-inductance of $0.05\text{ H}$. What is the e.m.f. induced in it if the current changes at a rate of $100\text{ A/s}$?

The energy stored in an inductor is in the form of:

If the length of a solenoid is doubled while keeping the number of turns and area constant, its self-inductance:

The unit of the rate of change of magnetic flux is:

The phenomenon of self-induction is also called the 'back e.m.f.' because:

Two coils are wound on each other. The self-inductance of each coil is $0.2\text{ H}$. If the coefficient of coupling is $0.9$, the mutual inductance is:

If the current in an inductor is changing at a constant rate, the induced e.m.f. is:

In the circuit shown, the switch $S$ is closed at $t = 0$. The battery has an EMF $V$ and negligible internal resistance. The inductor has a self-inductance $L = 12\ \text{mH}$, and the resistors have resistances $R_1 = 10\ \Omega$ and $R_2 = 15\ \Omega$. After the switch is closed, the current through the inductor $L$ grows toward its steady-state value. The time constant $\tau$ of this growth process is:

A pair of adjacent coils has a mutual inductance of $1.5$ H. If the current in one coil changes from $0$ to $20$ A in $0.5$ s, the change in flux linkage with the other coil is:

What happens to the self-inductance of a coil if an iron core is replaced by an aluminum core (paramagnetic)?

The total number of magnetic field lines passing through an area is called:

Which of these is necessary for electromagnetic induction in Faraday's experiments?

The discovery of electromagnetic induction led to the development of:

What is the value of flux when the area vector is at $180^{\circ}$ to the magnetic field?

If the primary coil in the third experiment is moved away from the secondary coil while current is steady, will there be an induced current?

Faraday’s second experiment proved that induction does not require a 'magnet' specifically, but rather a:

Which physical quantity's change is the ultimate cause of induced emf in all of Faraday's experiments?

In a laboratory demonstration of Faraday's experiment, a magnet is dropped through a coil. If the coil is not a closed loop (has a small gap), what is the observation?

Faraday's and Henry's experiments showed that the induced emf depends on the 'rate of change of magnetic flux'. If the flux $\phi$ through a loop changes according to $\phi(t) = at^2 - bt + c$, at what time $t$ is the induced emf zero?

In Faraday's experiment, the direction of induced current is such that it creates a magnetic field that opposes the change in flux. This is essentially a statement of:

Which of the following describes the flux through a surface parallel to the magnetic field?

A loop of area $10 \text{ cm}^2$ is placed in a field of $1 \text{ T}$. If the field is perpendicular to the loop plane, the flux is:

Magnetic flux is proportional to:

If a magnetic field $B$ acts at an angle of $90^\circ$ to the area vector of a surface, the flux is:

A small circular loop of radius $r$ is placed at the center of a large circular loop of radius $R$ ($r \ll R$) such that they are coplanar. If a constant current $I$ flows through the larger loop, the magnetic flux $\Phi$ linked with the smaller loop depends on the radii as:

A square loop of side $L$ is bent at its middle such that the two resulting rectangular halves are inclined at $90^{\circ}$ to each other. The loop is placed in a uniform magnetic field $B$ directed such that it makes an angle of $45^{\circ}$ with the normal to each half. The total magnetic flux through the loop is:

Which of the following is the correct expression for magnetic flux in terms of magnetic vector potential $\vec{A}$ and a path $dl$ bounding the surface $S$?

A planar conducting loop is shaped as a sector of a circle with radius $R$ and a central angle of $60^\circ$. The loop is placed in the $xy$-plane with its vertex at the origin $(0,0,0)$ and its radial sides at $\theta = 0$ and $\theta = \pi/3$. A non-uniform magnetic field exists in the region, given by $\vec{B} = B_0 \frac{\sqrt{x^2+y^2}}{R} \hat{k}$, where $B_0$ is a constant. The total magnetic flux linked with the loop is:

If the magnetic field $\vec{B}$ is uniform, the magnetic flux through any closed surface is always:

A coil of wire with $N$ turns is displaced in a time $\Delta t$ from a region where the magnetic flux per turn is $\Phi_1$ to a region where it is $\Phi_2$. The induced charge $Q$ in the circuit of resistance $R$ is:

The polarity of the induced emf in an AC generator changes after every:

What provides the torque to rotate the armature in a hydroelectric power plant?

The total number of magnetic field lines passing through a given area is called:

Which of these devices operates on the same principle as the AC generator?

The maximum magnetic flux linked with a coil is $\Phi_m$. If the coil is rotated with angular velocity $\omega$, the maximum induced EMF is:

What is the relation between the angular velocity $\omega$ and the frequency $f$ of the rotation of the generator armature?

In an AC generator, as the coil rotates from a position where its plane is parallel to the field to a position where its plane is perpendicular to the field, the induced EMF:

When an AC generator is in an open-circuit state, the torque required to keep it rotating (neglecting friction) is:

A coil of area $A$ and $N$ turns rotates with $\omega$ in field $B$. At $t = 0$, $\theta = 0$ (angle between $B$ and $A$). The EMF at any time $t$ is:

If the slip rings of an AC generator are replaced by a commutator, the output will be: