A long straight wire carries 10 A d.c. current an electron travels perpendicular to the plane of this wire at a distance 0.1 m with velocity  5.0 x 10⁶ ms^-1. Force acting on the electron due to current in wire is

• zero N

• 0·6 × 10^-17 N

• 2.4 × 10^-17 N

• 2.2 × 10^-17 N

Assertion:  A charged particle free to move in an electric field always moves along an electric field line. 

Reason: The electric field lines diverge from a negative charge and converge at a positive charge.

• 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:  If an electron and proton possessing same kinetic energy enter an electric field in a perpendicular direction, the path of the electron is more curved than that of the proton. 

Reason:  Electron forms a larger curve due to its small mass.

• 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:  Magnetic field is useful in producing parallel beam of charged particle. 

Reason:  Magnetic field inhibits the motion of charged particle moving across it.

• 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.

A wire of mass 100 g, length 1 m and current 5 A is balanced in mid air by a magnetic field B, then find the value of B

• 0.2 T

• 0.1 T

• 0.5 T

• 0.6 T

A toroid with mean radius r₀, diameter 2a have turns carrying current I. What is the magnetic field B outside the toroid?

• $\frac{\mathrm{N} \mathrm{I}}{2{\mathrm{\pi r}}_0}$

• $\frac{\mathrm{NI}}{2\mathrm{\pi } \left({\mathrm{r}}_0 + \mathrm{a}\right)}$

• $\frac{\mathrm{NI}}{\mathrm{\pi }\left({\mathrm{r}}_0 + \mathrm{a}\right)}$

• zero

Identify incorrect for electric charge q

• quantised

• conserved

• additive

• non-transferable

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.

239.

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.}}}$

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.