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UPCET / UPSEE Electromagnetism — practice questions

Explore 89 free Electromagnetism questions in UPCET / UPSEE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Electromagnetism questions and exercises with answers

Showing questions 1–30 of 89.

What is the electric field at the centre of a hollow conducting sphere of radius $R$ carrying total charge $Q$?Read the answer and worked solution →A circular coil of radius $R$ carries current $I$. The magnetic field at the centre of the coil is:Read the answer and worked solution →Gauss's law for electric flux through a closed surface enclosing total charge $q$ is:Read the answer and worked solution →The electric field intensity at any point **inside** a uniformly charged hollow conducting sphere is:Read the answer and worked solution →The SI unit of capacitance is:Read the answer and worked solution →Electrostatic potential due to a point charge $q$ at distance $r$ in vacuum is:Read the answer and worked solution →An electric dipole of moment $\vec p$ is placed in a uniform external field $\vec E$. The torque on it is:Read the answer and worked solution →Under electrostatic equilibrium, the net electric field in the **interior** of a conductor is:Read the answer and worked solution →An equipotential surface in any electric field is:Read the answer and worked solution →When $n$ identical capacitors of capacitance $C$ are connected in series, the equivalent capacitance is:Read the answer and worked solution →The dipole moment $\vec p$ of a pair of charges $+q$ and $-q$ separated by $2\ell$ is directed:Read the answer and worked solution →Three capacitors of 4 μF each are connected: two in parallel, that combination in series with the third. The equivalent capacitance is:Read the answer and worked solution →Which of the following molecules is **non-polar** (has zero permanent dipole moment)?Read the answer and worked solution →For a linear isotropic dielectric, the polarization $\vec P$ produced by an applied field $\vec E$ is:Read the answer and worked solution →Work done in moving a 6 C charge between two points raises the system's potential energy by 120 J. If the starting potential is 10 V, the final potential is:Read the answer and worked solution →The SI unit of electric charge is the:Read the answer and worked solution →Coulomb's law: force between two point charges is proportional to:Read the answer and worked solution →The value of k in Coulomb's law (in SI) is approximately:Read the answer and worked solution →Electric field strength at a point is defined as force per unit:Read the answer and worked solution →Total electric flux through a closed surface enclosing charge q (Gauss's law) is:Read the answer and worked solution →Electric field due to an INFINITE SHEET of charge with surface charge density σ:Read the answer and worked solution →The principle that charge can be neither created nor destroyed is:Read the answer and worked solution →Two point charges +2μC and -3μC are separated by 30 cm. The force on each (k = 9 × 10⁹):Read the answer and worked solution →Electric field due to a point charge q at distance r:Read the answer and worked solution →A charge of 1 C placed in an electric field of 100 N/C experiences force:Read the answer and worked solution →Electric potential V due to point charge q at distance r:Read the answer and worked solution →Potential difference between two points is 12 V. Work done to move 2 C between them:Read the answer and worked solution →Electric field INSIDE a conductor in electrostatic equilibrium is:Read the answer and worked solution →At an axial point of an electric dipole at distance r >> a (a = dipole half-length, p = qa·2 the dipole moment), E equals:Read the answer and worked solution →Number of charges that can be enclosed in a Gaussian surface in vacuum:Read the answer and worked solution →

Worked practice questions

What is the electric field at the centre of a hollow conducting sphere of radius $R$ carrying total charge $Q$?

  1. $0$
  2. $\dfrac{kQ}{R^2}$
  3. $\dfrac{kQ}{R^3}$
  4. $\dfrac{kQ}{R}$
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Correct answer: A. $0$

Inside any closed conducting shell with all charge residing on its outer surface, Gauss's law applied to a sphere of radius $r < R$ encloses zero charge so $E = 0$ everywhere inside the cavity.

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A circular coil of radius $R$ carries current $I$. The magnetic field at the centre of the coil is:

  1. $B = \dfrac{\mu_0 I}{2\pi R}$
  2. $B = \mu_0 I R$
  3. $B = \dfrac{\mu_0 I}{2 R}$
  4. $B = \dfrac{\mu_0 I}{4\pi R}$
Show answer and solution

Correct answer: C. $B = \dfrac{\mu_0 I}{2 R}$

From Biot-Savart's law applied to a circular loop of radius $R$ carrying current $I$, the field at the loop's centre is $B = \dfrac{\mu_0 I}{2 R}$. Direction along the axis of the loop. Right-hand rule again — curl fingers along current, thumb gives field direction. The field along the axis at distance $x$ from the centre is $B(x) = \dfrac{\mu_0 I R^2}{2(R^2 + x^2)^{3/2}}$, which collapses to the centre formula when $x = 0$.

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Gauss's law for electric flux through a closed surface enclosing total charge $q$ is:

  1. $\oint \vec{E}\cdot d\vec{s} = \varepsilon_0 / q$
  2. $\oint \vec{E}\cdot d\vec{s} = q / \varepsilon_0$
  3. $\oint \vec{E}\cdot d\vec{s} = q / (4\pi\varepsilon_0)$
  4. $\oint \vec{E}\cdot d\vec{s} = q\varepsilon_0$
Show answer and solution

Correct answer: B. $\oint \vec{E}\cdot d\vec{s} = q / \varepsilon_0$

Gauss's law: total electric flux through any closed (Gaussian) surface equals $q/\varepsilon_0$, where $q$ is the net charge enclosed.

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