31.

Two wires carrying

• Parallel current repel each other.

• Antiparallel current attract each other.

• Antiparallel current repel each other.

• Equal magnitudes of antiparallel current attract each other.

Electric field outside a long wire carrying charge q is proportional to

• $\frac{1}{\mathrm{r}}$

• $\frac{1}{{\mathrm{r}}^2}$

• $\frac{1}{{\mathrm{r}}^{{\displaystyle \raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$5$}\right.}}}$

• $\frac{1}{{\mathrm{r}}^{{\displaystyle \raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$2$}\right.}}}$

An electron projected with velocity $\overrightarrow{\mathrm{v}} = {\mathrm{v}}_0 \hat{\mathrm{i}}$ in the electric field $\overrightarrow{\mathrm{E}} = {\mathrm{E}}_0 \hat{\mathrm{j}}$. Trace the path followed by the electron E₀.

• Parabola

• Circle

• Straight line in + y direction.

• Straight line in -y direction

Calculate I for the given circuit diagram.

• 10 A

• 5 A

• 2.5 A

• 20 A

The frequency order for X-rays ( A), γ-rays (B), UV rays (C) is

• B > A > C

• A > B  > C

• C > B > A

• A > C > B

Find the voltage drop across a capacitor connected with a resistance and a battery of 60 V in series after a long time.

• 0V

• 60 V

• 30 V

• 38 V

Assertion:  Magnetic force is always perpendicular to the magnetic field.

Reason:  Electric force is along the direction of electric field.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  A planar circular loop of area A and carrying current I is equivalent to magnetic dipole of dipole moment M = IA.

Reason: At large distances, magnetic field of circular loop and magnetic dipole is same.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  A superconductor is a perfect diamagnetic substance.

Reason:  superconductor is a perfect conductor.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: A electrostatic field line never form closed loop.

Reason: Electrostatic field is conservative field.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.