Electromagnetism Concepts Quiz

The SI unit for electric charge is the coulomb (C), named after Charles-Augustin de Coulomb, a French physicist who studied electrostatic forces.

The angle between an equipotential surface and the electric field is always 90 degrees. This is because the electric field lines are always perpendicular to the equipotential surfaces. Imagine a hill, the electric field lines are like the slopes and the equipotential surfaces are like the contours.

The resistivity of a metal increases with temperature because the increased thermal motion of the atoms within the metal causes more frequent collisions between the electrons and the atoms, hindering the flow of electrons.

A moving coil galvanometer can be converted into a voltmeter by connecting a high resistance in series with the galvanometer. This is because the voltage across the galvanometer is proportional to the current flowing through it. By adding a high resistance, the current is reduced, and the voltage across the galvanometer is increased.

When a bar magnet is suspended freely, it aligns itself with the Earth's magnetic field, pointing from the magnetic south pole to the magnetic north pole, which is roughly aligned with the geographic north-south direction. The magnetic north pole of the magnet is attracted to the Earth's geographic north.

The energy stored in an inductor of inductance L when a current I is established is given by 1/2 * L * I^2. This energy represents the work done to build up the magnetic field within the inductor.

The direction of current induced in the loop 'abc' will be along the direction of 'abc' if the current I is increasing. This can be determined using Lenz's Law, which states that the induced current opposes the change in magnetic flux. The increasing current creates a magnetic field that opposes the field generated by the loop.

An ideal step-up transformer increases the voltage, but it decreases the current to maintain constant power. You can't get something for nothing! The power input to the transformer is equal to the power output (ignoring losses).

Displacement current is not due to the movement of charges, but rather the changing electric field. James Clerk Maxwell proposed this current to ensure continuity in electric fields.

An object placed between a concave mirror and its focal point will form a virtual, enlarged, and upright image. The image is virtual because the light rays do not actually converge at the image location.

The intensity of unpolarized light passing through two polarizers with their pass-axes inclined at an angle θ is given by I = I0 * cos^2(θ). This is known as Malus's Law. Think of the polarizers as filters letting through only light waves vibrating in a specific direction.

Thermionic emission is the process of emitting electrons from a metal surface due to heating the material. As the metal is heated, its electrons gain energy and can overcome the work function, escaping into the surrounding space.

Most alpha particles pass through a thin gold foil undeflected because the atom is mostly empty space. Ernest Rutherford's gold foil experiment led to this discovery.

Nuclei with the same atomic number, which is the number of protons, are called isotopes. This means that isotopes of an element have the same chemical properties but different masses due to the varying number of neutrons.

Conductors have almost zero energy band gap (E = 0 eV), allowing electrons to freely move through the material. Insulators have a large energy band gap (E > 3 eV), prohibiting electron movement. Semiconductors have a small energy band gap (E < 3 eV), allowing conduction under specific conditions.

A molecule with a permanent dipole moment is called a polar molecule. This means the molecule has an uneven distribution of charge, creating a positive and negative end. Think of the molecule as a tiny magnet.

The net magnetic flux through any closed surface is zero. This is a consequence of Gauss's law for magnetism, which states that magnetic monopoles do not exist.

A rotating vector representing alternating quantities, such as voltage or current, is called a phasor. Think of a rotating arrow that changes in magnitude and direction to represent the sinusoidal nature of AC signals.

A wavefront is a surface where all points on the wave are in the same phase. It represents a region of constant phase. Think of it as a 'snapshot' of the wave at a specific moment in time.

Light, particularly in its interaction with matter, exhibits wave-particle duality, behaving as if it's composed of packets of energy called photons.

Gauss's law in electrostatics states that the total electric flux through any closed surface is proportional to the enclosed electric charge. This means the electric field lines start on positive charges and end on negative charges.

Drift velocity is the average velocity of free electrons in a conductor under the influence of an electric field. Mobility is the ratio of drift velocity to the electric field, representing how easily electrons move in a material. Think of drift velocity as the average speed of electrons in a current, and mobility as how easily electrons move through the material.

The magnetic field at the midpoint of an air-core solenoid is given by B = μ₀ * n * I, where μ₀ is the permeability of free space, n is the number of turns per unit length, and I is the current. This formula assumes the solenoid is long and cylindrical.

The AC generator's principle is based on electromagnetic induction. When a coil rotates in a magnetic field, a changing magnetic flux induces an electromotive force (EMF) in the coil. This EMF is alternating due to the coil's continuous rotation.

Ultraviolet radiation has applications in sterilization and medical treatments. UV light can kill bacteria and viruses, making it useful for sterilizing medical equipment and water. It can also be used for treating certain skin conditions.

Refracting telescopes use a convex lens as the objective, focusing light to form an image. Reflecting telescopes use a concave mirror as the objective, reflecting light to form an image.

Total internal reflection occurs when light travels from a denser medium to a rarer medium (e.g., water to air) at an angle greater than the critical angle. The light is reflected back into the denser medium. Imagine light bouncing off the bottom of a swimming pool.

In an n-type semiconductor, the majority charge carriers are electrons, and the minority charge carriers are holes. This type of semiconductor results from doping a pure semiconductor with a pentavalent element (e.g., arsenic).

Electric field lines can never cross each other, they always point in the direction of decreasing potential, and the density of field lines indicates the strength of the field. These properties help visualize electric fields.

The effective capacitance of two capacitors connected in parallel is the sum of their individual capacitances. Think of it as increasing the total amount of charge the capacitors can store.

The Lorentz force is the force experienced by a charged particle moving in a magnetic field. It is given by F = q (v x B), where q is the charge, v is the velocity, and B is the magnetic field. Think of the force pushing the charged particle perpendicular to its velocity and the magnetic field.

Diamagnetic materials are weakly repelled by magnetic fields, while paramagnetic materials are weakly attracted. They differ in how electrons are arranged and their magnetic moments in the absence of a field. Diamagnetic materials have paired electrons with opposing spins, while paramagnetic materials have unpaired electrons with aligned spins.

Electromagnetic induction can be demonstrated by moving a bar magnet into and out of a coil. When the magnet moves, the magnetic flux through the coil changes, inducing an electromotive force (EMF) in the coil. This EMF can be detected using a galvanometer.

Photoelectric effect experiments have shown that light consists of discrete packets of energy known as photons, the energy of which is proportional to the frequency of light. Also, the energy of a photon is required to overcome the work function of the metal, and the number of emitted electrons is proportional to the intensity of light.

Bohr's atomic model postulates that electrons orbit the nucleus in quantized energy levels, their energy is quantized and can only jump between discrete levels by absorbing or emitting photons, and the angular momentum of an electron is also quantized.

One atomic mass unit (u) is equivalent to 931.5 MeV (megaelectronvolt) of energy. This is calculated using Einstein's famous E=mc^2 equation, which relates energy and mass.

The electric field at a point on the axis of an electric dipole is given by E = (kp * 2p * r)/(r^2 - a^2)^2, where kp is the Coulomb constant, p is the dipole moment, r is the distance from the center of the dipole, and a is the distance between the charges. Think of the electric field as being stronger closer to the dipole and weaker further away.

For two cells connected in series, the effective emf is the sum of their individual emfs, and the effective internal resistance is the sum of their individual internal resistances. Think of combining the 'push' of the two cells and the 'resistance' within each cell when connected in series.

The magnetic field at a point on the axis of a circular current loop is given by B = (μ₀ * I * R^2)/(2 * (R^2 + x^2)^(3/2)), where μ₀ is the permeability of free space, I is the current, R is the radius of the loop, and x is the distance from the center of the loop along the axis. Think about the magnetic field lines forming circles around the loop.

The resultant displacement of two coherent waves with a phase difference of φ is given by R = √(A1^2 + A2^2 + 2 * A1 * A2 * cos(φ)), where A1 and A2 are the amplitudes of the waves. The phase difference determines whether the waves interfere constructively (in phase) or destructively (out of phase).

A rectifier converts alternating current (AC) into direct current (DC). A full-wave rectifier uses four diodes to rectify both positive and negative halves of the AC waveform, resulting in a DC output with a smaller ripple compared to a half-wave rectifier. Think of the diodes as one-way gates for current.

The potential at a point due to a charge q is given by V = kq/r, where k is Coulomb's constant and r is the distance from the charge. The work done in moving a charge Q from infinity to a point with potential V is W = Q * V. Think of the potential as the energy per unit charge at a point.

In the network provided, the current through the galvanometer (I3) can be calculated using Kirchhoff's laws. The current through the galvanometer is determined by the balance of currents in the branches of the Wheatstone bridge.

The current in an RL-C circuit will either lead or lag the voltage depending on the reactances of the inductor and capacitor. In this case, the inductive reactance (XL = 2πfL) is 314 Ω, and the capacitive reactance (XC = 1/(2πfC)) is 354 Ω. Since XC > XL, the current leads the voltage. The phase difference between the current and voltage is given by tan φ = (XC - XL)/R = 0.4, meaning the phase difference is approximately 21.8 degrees.

The refractive index of the prism can be determined using the formula n = sin((A + Dm)/2)/sin(A/2), where A is the prism angle and Dm is the angle of minimum deviation. In this case, n = 1.53. If the prism is placed in water, the angle of minimum deviation will change due to the change in the refractive index of the surrounding medium. The new minimum deviation can be calculated using the same formula but with the refractive index of water taken into account. In this case, the new angle of minimum deviation is approximately 25 degrees.