Physics of Electric Dipoles and Evaluation Criteria

The formula is $W = pE (cos \theta_0 - cos \theta_1)$.

The potential energy is maximum when the dipole moment $\mathbf{p}$ is antiparallel to the electric field $\mathbf{E}$, or when $\theta = 180°$.

The potential energy is given by $U(\theta) = - \mathbf{p} \cdot \mathbf{E}$, which can also be expressed as $U(\theta) = -pE cos \theta$.

<p>The torque is given by $\tau = pE sin \theta$.</p> Signup and view all the answers

<p>The potential energy of a dipole is at a minimum when $\theta = 0°$, which means the dipole moment is along the direction of the electric field.</p> Signup and view all the answers

<p>Marks should be awarded on the right-hand side for each part, and the total must be written in the left-hand margin and encircled.</p> Signup and view all the answers

<p>Marks should be awarded in the left-hand margin and encircled.</p> Signup and view all the answers

<p>The answer deserving more marks should be retained, while the other answer should be scored out with a note 'Extra Question'.</p> Signup and view all the answers

<p>No marks should be deducted for cumulative errors; they should be penalized only once.</p> Signup and view all the answers

<p>A full scale of marks from 0 to 70 must be utilized.</p> Signup and view all the answers

<p>Examiners should avoid leaving answers unassessed, giving incorrect marks, and wrong totaling.</p> Signup and view all the answers

<p>It should be marked with a cross (X) and awarded zero (0) marks.</p> Signup and view all the answers

<p>Examiners must evaluate 20 answer books per day in main subjects and 25 in other subjects.</p> Signup and view all the answers

<p>The power of one part of the lens will be $2P$.</p> Signup and view all the answers

<p>The power of the combination will be $2P$.</p> Signup and view all the answers

<p>The power of the combination will be $0$.</p> Signup and view all the answers

<p>The power of the combination is $15 D$.</p> Signup and view all the answers

<p>The formula is $P = 1/f$ where $f$ is the focal length in meters.</p> Signup and view all the answers

<p>The focal length of each part becomes half that of the original lens.</p> Signup and view all the answers

<p>The resulting power will be $2P$.</p> Signup and view all the answers

<p>A smaller radius of curvature leads to a higher lens power.</p> Signup and view all the answers

<p>The kinetic energy of emitted photoelectrons increases with the increase in the intensity of the incident light.</p> Signup and view all the answers

<p>The flux linkage between the two coils is maximum when they are wound on each other.</p> Signup and view all the answers

<p>The two wires, when carrying current in the same direction, attract each other and move apart.</p> Signup and view all the answers

<p>No, plane and convex mirrors cannot produce real images under any circumstance.</p> Signup and view all the answers

<p>Photoelectric current depends on the wavelength of the incident light.</p> Signup and view all the answers

<p>This illustrates the fundamental electromagnetic principle that like currents repel each other, while opposite currents attract.</p> Signup and view all the answers

<p>Using the wave speed equation, the wavelength can be determined, suggesting a relationship between frequency and wavelength.</p> Signup and view all the answers

<p>When the current direction is reversed, the wires repel each other, demonstrating the effects of electromagnetic forces.</p> Signup and view all the answers

<p>The formula is $R = R_0 [1 + eta (T - T_0)]$.</p> Signup and view all the answers

<p>The final temperature $T$ is $270°C$.</p> Signup and view all the answers

<p>The wavelength is $600 nm$ or $6×10^{-7} m$.</p> Signup and view all the answers

<p>The wavelength in the medium is $400 nm$ or $4×10^{-7} m$.</p> Signup and view all the answers

<p>In this context, $R$ represents the radius of the curved surface.</p> Signup and view all the answers

<p>The radius $R$ is $6.4 cm$.</p> Signup and view all the answers

<p>$R_1$ and $R_2$ are the radii of curvature for the two surfaces of a lens or mirror.</p> Signup and view all the answers

<p>The refractive index inversely affects the wavelength; as $μ$ increases, wavelength decreases.</p> Signup and view all the answers

<p>Flux leakage, resistance of the windings, and eddy currents.</p> Signup and view all the answers

<p>Current changes correspondingly, so the input power is equal to the output power.</p> Signup and view all the answers

<p>Vs = 1350 V.</p> Signup and view all the answers

<p>IP = 30 A.</p> Signup and view all the answers

<p>The minimum deviation angle is defined as the angle at which the angle of incidence equals the angle of emergence.</p> Signup and view all the answers

<p>n = sin(A + δ) / sin(A).</p> Signup and view all the answers

<p>The refracted ray becomes parallel to the base of the prism.</p> Signup and view all the answers

<p>Understanding energy losses is crucial for improving efficiency and performance of electrical systems.</p> Signup and view all the answers

The kinetic energy of photoelectrons released in the photoelectric effect is independent of the intensity of incident light. It is solely determined by the frequency of the incident light.

Photoelectric current, the flow of electrons emitted from a material due to the photoelectric effect, is directly proportional to the intensity of the incident light. More intense light means more photons, resulting in more electrons being ejected.

The mutual inductance between two coils is maximized when they are wound over each other, as this configuration maximizes the magnetic flux linkage between the coils, leading to a stronger inductive effect.

Two parallel wires carrying current in the same direction will attract each other. Conversely, two wires carrying current in opposite directions will repel each other. This is because the magnetic fields created by the wires interact with each other.

Plane and convex mirrors can only produce virtual images. These images cannot serve as an object for a real image, meaning a plane or convex mirror will never produce a real image.

The number of photons emitted from a source is directly proportional to the intensity of the light source. This means higher intensity light emits more photons.

Frequency is a measure of the number of wave cycles passing a point in one second. It determines the energy of a photon, with higher frequency resulting in higher energy.

The higher the frequency of light, the higher the energy carried by each photon. This is a key aspect of the electromagnetic spectrum, where higher frequency waves, like X-rays, carry much more energy than lower frequency waves, like radio waves.

The power of a lens is inversely proportional to its focal length. When a lens is cut in half, its focal length doubles, and therefore its power is halved.

When two lenses with the same power are placed in contact, the power of the combination is simply the sum of the individual powers.

The power of a double convex lens is directly proportional to its curvature. When the lens is cut in half along its principal axis, the curvature of one half is halved, leading to a reduction in power.

The power of a combination of lenses is the sum of the powers of the individual lenses. The power of each lens is determined by its focal length (P = 1/f).

The power of a lens is inversely proportional to its focal length. When two lenses are placed in contact, the combination has a focal length determined by 1/f = 1/f1 + 1/f2.

When two lenses with different powers are placed in contact, the total power of the combination is the sum of the individual powers. For example, if you have a lens with a power of +2D and another lens with a power of +3D, the combination will have a power of +5D.

The power of a lens is the reciprocal of its focal length, expressed in diopters (D). A lens with a power of +2D has a focal length of 0.5 meters.

The power of a lens is a measure of its ability to converge or diverge light rays. A converging lens (convex) has positive power, and a diverging lens (concave) has negative power.

If a question is divided into parts, award marks for each part separately and then add them up. Write the total encircled in the left margin.

If a question has no parts, award marks in the left margin and encircle them.

If a student answers more questions than required, choose the question with the most marks and discard the extra one. Note "Extra Question" next to the discarded answer.

If a student makes the same mistake multiple times, only deduct marks once.

Use the entire range of marks (0 to 70) to represent the student's evaluation.

Ensure each examiner evaluates for full working hours (8 hours/day) and a set number of papers per day.

Common errors to avoid during evaluation include: leaving answers unassessed, giving incorrect marks, wrong totaling of marks, wrong question-wise totaling, incorrect transfer of marks, wrong grand total, mismatched figures/words, incorrect online transfer, and marking correct answers without awarding corresponding marks.

If the answer is completely wrong, mark it with a cross (X) and give zero (0) marks.

The work done in rotating a dipole from an initial angle (θ₀) to a final angle (θ₁) in an external electric field is given by: W = pE(cos θ₀ - cos θ₁). This formula represents the change in potential energy of the dipole.

The potential energy (U) of a dipole in an electric field is defined as U = -pEcosθ, where p is the dipole moment, E is the electric field strength, and θ is the angle between the dipole moment and the electric field. It represents the stored energy due to the dipole's orientation in the field.

The potential energy of a dipole is maximum (highest stored energy) when the dipole moment (p) is antiparallel to the electric field (E). This configuration corresponds to an angle of 180° or π radians between p and E.

The potential energy of a dipole is minimum (lowest stored energy) when the dipole moment (p) is aligned with the electric field (E). This occurs when the angle between p and E is 0°.

The torque (τ) acting on a dipole in an electric field is given by τ = pE sin θ, where p is the dipole moment, E is the electric field strength, and θ is the angle between p and E. It represents the rotational force acting on the dipole.

The resistance of a material changes with temperature. The new resistance (R) at temperature T is calculated using the formula: R = R°(1 + α(T - T°)), where R° is the resistance at reference temperature T°, and α is the temperature coefficient of resistance.

The wavelength of light changes when it travels from one medium to another. The wavelength in the medium (λmedium) is calculated by dividing the wavelength in air (λair) by the refractive index (μ) of the medium: λmedium = λair / μ.

The lens maker's formula relates the focal length (f) of a lens to the radii of curvature (R1 and R2) of its surfaces and its refractive index (μ). The formula is: 1/f = (μ - 1)(1/R1 - 1/R2).

The speed of light (v) in a vacuum is constant, but it slows down when it passes through a medium. The speed of light in a medium is calculated by dividing the speed of light in a vacuum (c) by the refractive index (μ) of the medium: v = c / μ.

The wavelength (λ) of light is related to its frequency (ν) and speed (v) by the equation: v = νλ. When light travels from one medium to another, its frequency remains constant, but its speed and wavelength change.

In a vacuum, the speed of light is constant. The speed of light in a vacuum (c) is approximately 3 x 108 m/s.

The focal length of a lens is the distance from the center of the lens to the point where parallel rays of light converge after passing through the lens.

When light passes through a lens, its path is bent, and the amount of bending depends on the refractive index of the lens material and the curvature of the lens surfaces.

Flux leakage refers to the loss of magnetic flux from a magnetic circuit, reducing the magnetic field strength and efficiency of the system.

Resistance in the windings of an electrical device causes energy loss as heat due to the flow of current through the wires.

Eddy currents are circulating currents induced within a conducting material due to a changing magnetic field. These currents dissipate energy as heat, leading to losses.

Hysteresis is a phenomenon in magnetic materials where energy is lost due to the magnetization and demagnetization cycles. This occurs when the material's response to a changing magnetic field lags behind the change.

The ratio of the number of turns in the secondary winding (Ns) to the number of turns in the primary winding (NP) determines the voltage step-up or step-down ratio in a transformer.

In an ideal transformer with no energy loss, the input power (IP) is equal to the output power (IS). This means the current and voltage are inversely proportional.

The minimum deviation angle is the smallest angle of deviation a light ray experiences when passing through a prism. At this angle, the angle of incidence and the angle of emergence are equal.

The refractive index of a material is the ratio of the sine of the angle of incidence to the sine of the angle of refraction for a light ray passing from one medium to another. It describes how much light bends as it enters a medium.