Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12

# Question Bank Solutions for PUC Karnataka Science Class 12 - Department of Pre-University Education, Karnataka - Physics

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A circular coil of cross-sectional area 200 cm2 and 20 turns is rotated about the vertical diameter with angular speed of 50 rad s−1 in a uniform magnetic field of magnitude 3.0 × 10−2T. Calculate the maximum value of the current in the coil.

[4.02] Electromagnetic Induction
Chapter: [4.02] Electromagnetic Induction
Concept: Electromagnetic Induction Questions

Calculate the dimensions of (a) $\int \overrightarrow{E} . d \overrightarrow{l,}$ (b) vBl and (c) $\frac{d \Phi_B}{dt}.$ The symbols have their usual meaning.

[4.02] Electromagnetic Induction
Chapter: [4.02] Electromagnetic Induction
Concept: Electromagnetic Induction Questions

A conducting square loop having edges of length 2.0 cm is rotated through 180° about a diagonal in 0.20 s. A magnetic field B exists in the region which is perpendicular to the loop in its initial position. If the average induced emf during the rotation is 20 mV, find the magnitude of the magnetic field.

[4.02] Electromagnetic Induction
Chapter: [4.02] Electromagnetic Induction
Concept: Electromagnetic Induction Questions

Why does a compass needle get deflected when brought near a bar magnet?

[3.01] Magnetism and Matter
Chapter: [3.01] Magnetism and Matter
Concept: Introduction of Magnetism

If Coulomb’s law involved 1/r3 dependence (instead of 1/r2), would Gauss’s law be still true?

[1.02] Electric Charges and Fields
Chapter: [1.02] Electric Charges and Fields
Concept: Gauss’s Law

Draw a labelled diagram of an ac generator.

[4.02] Electromagnetic Induction
Chapter: [4.02] Electromagnetic Induction
Concept: AC Generator

Obtain the expression for the emf induced in the rotating coil of N turns each of cross-sectional area A, in the presence of a magnetic field vecB .

[4.02] Electromagnetic Induction
Chapter: [4.02] Electromagnetic Induction
Concept: AC Generator

Why should the objective of a telescope have large focal length and large aperture? Justify your answer.

[6.01] Ray Optics and Optical Instruments
Chapter: [6.01] Ray Optics and Optical Instruments
Concept: Optical Instruments > Telescope

Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment.

[6.01] Ray Optics and Optical Instruments
Chapter: [6.01] Ray Optics and Optical Instruments
Concept: Optical Instruments > Telescope

You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope ? Give reason

 Lenses Power (D) Aperture (cm) L1 3 8 L2 6 1 L3 10 1
[6.01] Ray Optics and Optical Instruments
Chapter: [6.01] Ray Optics and Optical Instruments
Concept: Optical Instruments > Telescope

In the figure given below the input waveform is converted into the output waveform by a device ‘X’. Name the device and draw its circuit diagram.

[9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits
Chapter: [9.01] Semiconductor Electronics - Materials, Devices and Simple Circuits
Concept: Integrated Circuits

Describe briefly, with the help of a labelled diagram, the basic elements of an A.C. generator.

[4.02] Electromagnetic Induction
Chapter: [4.02] Electromagnetic Induction
Concept: AC Generator

State A.C. generator underlying principle?

[4.02] Electromagnetic Induction
Chapter: [4.02] Electromagnetic Induction
Concept: AC Generator

A thin conducting spherical shell of radius R has charge Q spread uniformly over its surface. Using Gauss’s law, derive an expression for an electric field at a point outside the shell.

[1.02] Electric Charges and Fields
Chapter: [1.02] Electric Charges and Fields
Concept: Gauss’s Law

Draw a graph of electric field E(r) with distance r from the centre of the shell for 0 ≤ r ≤ ∞.

[1.02] Electric Charges and Fields
Chapter: [1.02] Electric Charges and Fields
Concept: Gauss’s Law

Is the colour of 620 nm light and 780 nm light same? Is the colour of 620 nm light and 621 nm light same? How many colours are there in white light?

[6.02] Wave Optics
Chapter: [6.02] Wave Optics
Concept: Introduction of Wave Optics

The wavelength of light in a medium is $\lambda = \lambda_0 /\mu,$ where $\lambda$ is the wavelength in vacuum. A beam of red light $\left( \lambda_0 = 720\text{ nm} \right)$ enters water. The wavelength in water is $\lambda = \lambda_0 /\mu = 540\text{ nm.}$ To a person under water, does this light appear green?

[6.02] Wave Optics
Chapter: [6.02] Wave Optics
Concept: Introduction of Wave Optics

If we put a cardboard (say 20 cm × 20 cm) between a light source and our eyes, we can't see the light. But when we put the same cardboard between a sound source and out ear, we hear the sound almost clearly. Explain.

[6.02] Wave Optics
Chapter: [6.02] Wave Optics
Concept: Introduction of Wave Optics

TV signals broadcast by a Delhi studio cannot be directly received at Patna, which is about 1000 km away. But the same signal goes some 36000 km away to a satellite, gets reflected and is then received at Patna. Explain.

[6.02] Wave Optics
Chapter: [6.02] Wave Optics
Concept: Introduction of Wave Optics

Is it necessary to have two waves of equal intensity to study interference pattern? Will there be an effect on clarity if the waves have unequal intensity?

[6.02] Wave Optics
Chapter: [6.02] Wave Optics
Concept: Introduction of Wave Optics
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