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.

76.

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.

What is the dimensions of a magnetic field B in terms of C ( = coulomb ), M, L, T?

• [ M¹ L^-1 T^-2 C ]

• [ M¹ L⁰ T^-1 C^-1 ]

• [ M¹ L⁰ T^-2 C ]

• [ M¹ L⁰ T^-1 C ]

Magnetic energy per unit volume is represented by

• $\frac{{\mathrm{B}}^2}{2 {\mathrm{\mu }}_0}$

• $\frac{{\mathrm{B}}^2}{2 {\mathrm{\mu }}_0^{ 2}}$

• $\frac{2 {\mathrm{B}}^2}{{\mathrm{\mu }}_0}$

• $\frac{{\mathrm{B}}^2}{{\mathrm{\mu }}_0}$

Magnetic field at ' $𝑎$' distance a from long currying current wire is proportional to

• $\frac{1}{𝑎}$

• $\frac{1}{{𝑎}^2}$

• $\frac{1}{\sqrt{𝑎}}$

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