Q.(a) How many electrons constitute an electric charge of – 16 μC ?

Showing the 12 most recent of 16 on this concept.

1. CBSE 2026Set ANNUAL1 markMCQ
   Q.The size of ideal dipole is :

   (a) Zero

   (b) Infinite

   (c) One

   (d) None of the above

   ›Reveal solutionSolution

   An ideal dipole is the point-dipole limit: separation → 0 with dipole moment finite, so its size is zero.

   An electric dipole consists of two equal and opposite charges +q and −q separated by a small distance 2a, with dipole moment p = q(2a). An 'ideal' (or point) dipole is the mathematical limit in which the separation 2a is made vanishingly small (2a → 0) while simultaneously making q very large …

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2. CBSE 2025Set X11 mark
   Q.An electric dipole placed in a uniform electric field experiences a net ________.

   ›Reveal solutionSolution

   torque In a uniform field the forces on the two charges of the dipole are equal and opposite, so the net force is zero, but they act along different lines and constitute a couple that produces a …

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3. CBSE 2025Set ANNUAL1 mark
   Q.[Case/Source-based passage] An electric dipole consists of two charges $+q$ and $-q$ separated by a small distance $2a$. Its total charge is zero. It is characterized by a dipole moment vector $\vec{p}$ whose magnitude is $q\times 2a$ and which points in the direction from $-q$ to $+q$.

   (i) Write the unit of electric dipole moment.

   ›Reveal solutionSolution

   Dipole moment $p=q\times2a$ has units of charge $\times$ distance.

   The electric dipole moment is defined as $p = q\times(2a)$, the product of the magnitude of either charge and the separation between the two charges. Since charge is measured in coulombs (C) and separation in metres (m), the SI unit …

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4. CBSE 2025Set ANNUAL1 mark
   Q.[Case/Source-based passage] An electric dipole consists of two charges $+q$ and $-q$ separated by a small distance $2a$. Its total charge is zero. It is characterized by a dipole moment vector $\vec{p}$ whose magnitude is $q\times 2a$ and which points in the direction from $-q$ to $+q$.

   (iii) What is polar molecule?

   ›Reveal solutionSolution

   Polar molecules have a built-in charge asymmetry that gives them a permanent dipole moment.

   A polar molecule is one in which the centre of the positive charge distribution and the centre of the negative charge distribution do not coincide, due to the asymmetric arrangement of atoms and the unequal sharing of electrons between them (unequal electronegativities). As a result, such a molecule possesses a permanent (built-in) electric dipole moment, which exists even in the absence of any external electric field. Common examples include water (H₂O), HCl, and NH₃. This is in contrast to a non-polar molecule (like $\text{O}_2$ or $\text{CO}_2$), where the positive and negative charge centres coincide, giving zero perma …

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5. CBSE 2025Set ANNUAL1 mark
   Q.Define the electric dipole moment.

   ›Reveal solutionSolution

   An electric dipole moment measures the strength and orientation of a pair of equal and opposite charges separated by a small distance.

   An electric dipole consists of two equal and opposite point charges $+q$ and $-q$ separated by a small distance $2a$. Its electric dipole moment is defined as the vector:

   $\vec{p} = q(2\vec{a})$

   …

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6. CBSE 2025Set ANNUAL1 markMCQ
   Q.What orientation of an electric dipole in uniform electric field is said to be in stable equilibrium ?

   (a) θ = 0

   (b) θ = 90

   (c) θ = 120

   (d) θ = 180

   ›Reveal solutionSolution

   A dipole is in stable equilibrium when its dipole moment is parallel to the field, i.e. θ = 0°.

   The torque on a dipole in a uniform field is $\tau = pE\sin\theta$, and its potential energy is $U = -pE\cos\theta$.

   Both θ = 0° and θ = 180° give zero torque (equilibrium positions), but they are not equally stable:

   • At θ = 0°, $U = -pE$ (minimum energy) → any small angular displacement creates a restoring torque that brings p back to alignment with E. This is stable equilibrium. …

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7. CBSE 2024Set A11 markMCQ
   Q.The electric dipole placed in uniform electric field is unstable, if the angle between electric field and dipole moment is

   (a) $0^\circ$

   (b) $60^\circ$

   (c) $90^\circ$

   (d) $180^\circ$

   ›Reveal solutionSolution

   (d) $180^\circ$ …

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8. CBSE 2024Set IMPROVEMENT1 markMCQ
   Q.Assertion (A): In water molecule H$_2$O there is permanent dipole moment even in absence of external electric field. Reason (R): In some molecules the centres of negative and positive charges do not coincide.

   (a) Both A and R are correct and R is the correct explanation of A.

   (b) Both A and R are correct but R is not the correct explanation of A.

   (c) A is correct but R is incorrect.

   (d) Both A and R are incorrect.

   ›Reveal solutionSolution

   Water is a polar molecule because its bent geometry separates the centres of positive and negative charge, giving it a permanent dipole moment.

   Assertion (A) is correct: the water molecule H$_2$O possesses a permanent electric dipole moment even without any external field, because it is a polar molecule. Reason (R) is also correct: a permanent dipole moment arises in molecules whose positive and negative charge centres do not coincide — in H$_2$O, the bent (non-linear) shape of the molecule means the centre of the negative charge (near the oxygen) does …

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9. CBSE 2023Set F1 markMCQ
   Q.What is the angle between the electric dipole moment P and the electric field strength E when the dipole is in a stable equilibrium? (A) pi/4 (B) pi (C) pi/2 (D) 0

   ›Reveal solutionSolution

   Stable equilibrium ⇒ P parallel to E ⇒ angle = 0.

   The potential energy of a dipole in a uniform field is $U = -pE\cos\theta$, and the torque is $\tau = pE\sin\theta$.

   • At $\theta = 0$: $\tau = 0$ and $U = -pE$ (minimum energy) → stable equilibrium. …

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10. CBSE 2022Set M1 mark
    Q.Define 'electric dipole moment'.

    ›Reveal solutionSolution

    Dipole moment = charge × separation, directed −q → +q.

    An electric dipole is a pair of equal and opposite charges $+q$ and $-q$ separated by a small distance $2a$.

    The electric dipole moment is defined as the product of the magnitude of either charge and the distance of separation between them:

    $\vec{p} = q \,(2\vec{a})$ …

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11. CBSE 2022Set ANNUAL1 mark
    Q.Write SI unit and dimensional formula of electric dipole moment.

    ›Reveal solutionSolution

    Electric dipole moment p = q × 2a; its unit follows directly from charge × length, and its dimensional formula follows from [charge] = [A T] and [length] = [L].

    The electric dipole moment of a pair of equal and opposite charges +q and −q separated by a distance 2a is defined as

    $p = q \times 2a$

    directed from the negative to the positive charge.

    SI unit: Since q is in coulomb (C) and 2a is in metre (m), the unit of p is coulomb-metre (C·m).

    …

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12. CBSE 2021Set ANNUAL1 mark
    Q.Whether electric dipole moment is a vector or a scalar quantity? Write the SI unit of electric dipole moment.

    ›Reveal solutionSolution

    Dipole moment has both magnitude and direction (from negative to positive charge), so it is a vector, measured in C·m.

    An electric dipole consists of two equal and opposite charges $+q$ and $-q$ separated by a distance $2a$. Its dipole moment is defined as

    $\vec{p} = q(2a)\,\hat{n}$ …

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