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Physics Case study (4 Marks)

MODEL PAPER 9 · CBSE STD 12 Science (CBSE - English Medium). 2 questions.

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Case study (4 Marks)

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Question 14 Marks
Electric dipole consist of a pair of equal and opposite point charges separated by a small distance and its strength is measured by the dipole moment. The field around the dipole in which the electric effect of the dipole can be experienced is called the dipole field. 
Image
(i) The electric dipole moment is:
(a) a scalar quantity
(b) neither scalar nor vector quantity
(c) a vector quantity

(ii)Electric field due to the electric dipole is
(a) cylindrically symmetric (b) spherically symmetric (c) symmetric (d) asymmetric

(iii) The SI unit of dipole moment is:
(a) $C / m$ (b) C-m (c) $c / m ^2$ (d) $C - m ^2$

(iv) Charges $\pm 20 nC$ are separated by 5 mm . calculate the magnitude of dipole moment:-
(a) $10^{-7} C - m$ (b) $10^{10} C - m$ (c) $10^{-10} C - m$ (d) $10^{-8} C - m$

OR

When an electric dipole is placed in a uniform electric field, it experiences
(a) Neither any force nor any torque
(b) Force but no torque
(c) Force as well as torque
(d) Torque but no net force
Answer
Electric dipole consist of a pair of equal and opposite point charges separated by a small distance and its strength is measured by the dipole moment. The field around the dipole in which the electric effect of the dipole can be experienced is called the dipole field. 
Image
(i) (c) a vector quantity
Explanation: a vector quantity

(ii) (a) cylindrically symmetric
Explanation: cylindricaly symmetric

(iii) (b) C-m
Explanation: C-m

(iv) (c) $10^{-10} C - m$
Explanation: $10^{-10} C - m$

OR

(d) Torque but no net force
Explanation: Torque but no net force
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Question 24 Marks
In an electromagnetic wave both the electric and magnetic fields are perpendicular to the direction of propagation, that is why electromagnetic waves are transverse in nature. Electromagnetic waves carry energy as they travel through space and this energy is shared equally by the electric and magnetic fields. Energy density of an electromagnetic waves is the energy in unit volume of the space through which the wave travels.
(i) The electromagnetic waves propagated perpendicular to both $\vec{E}$ and $\vec{B}$. The electromagnetic waves travel in the direction of
(a) $\vec{E} \cdot \vec{B}$
(b) $\vec{B} \cdot \vec{E}$
(c) $\vec{E} \times \vec{B}$
(d) $\vec{B} \times \vec{E}$

(ii) Fundamental particle in an electromagnetic wave is
(a) photon (b) phonon (c) electron (d) proton

(iii) Electromagnetic waves are transverse in nature is evident by
(a) diffraction (b) interference (c) polarisation (d) reflection

OR

The electric and magnetic fields of an electromagnetic waves are
(a) in opposite phase and parallel to each other
(b) in phase and parallel to each other.
(c) in phase and perpendicular to each other
(d) in opposite phase and perpendicular to each other

(iv) d) in opposite phase and perpendicular to each other
(a) frequency (b) wavelength (c) velocity (d) all these depend on each other
Answer
In an electromagnetic wave both the electric and magnetic fields are perpendicular to the direction of propagation, that is why electromagnetic waves are transverse in nature. Electromagnetic waves carry energy as they travel through space and this energy is shared equally by the electric and magnetic fields. Energy density of an electromagnetic waves is the energy in unit volume of the space through which the wave travels. (i) (c) $\vec{E} \times \vec{B}$
Explanation: Electromagnetic waves propagate in the direction of $\vec{E} \times \vec{B}$.

(ii) (a) photon
Explanation: Photon is the fundamental particle in an electromagnetic wave

(iii) (c) polarisation
Explanation: Polarisation establishes the wave nature of electromagnetic waves.

OR

(c) in phase and perpendicular to each other
Explanation: The electric and magnetic fields of an electromagnetic wave are in phase and perpendicular to each other.

(iv) (c) in phase and perpendicular to each other
Explanation: The electric and magnetic fields of an electromagnetic wave are in phase and perpendicular to each other.

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Case study (4 Marks) - Physics STD 12 Science Questions - Vidyadip