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 charged particle can be accelerated in a cyclotron by the alternate distribution of the field.

Reason: Energy of the charged particle is increased by the field applied. 

• 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:  At rest, radium is decayed into Radon and an $\mathrm{\alpha }$-particle. They both moves back to back of each other. 

Reason: Splitting of radioactive particle is based on conservation of linear momentum.

• 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: Gauss's law shows diversion when inverse square law is not obeyed.

Reason: Gauss's law is a consequence of conservation of charges.

• 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:  Gauss's law can't be used to calculate electric field near electric an electric dipole.

Reason: Electric dipole don't have symmetrical charge distribution.

• 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 correct explaination of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion:  An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube. 

Reason:  Electric field requires low voltage.

• 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.

147.

Four charges arc arranged at the corners of a square as shown in the figure. The direction of electric field at the centre of the square is along

 

• DC

• BC

• AB

• AD

Electric field at the centre of a uniformly charged semicircle of radius a is

• $\frac{\mathrm{\lambda }}{2{\mathrm{\pi \epsilon }}_0{\mathrm{a}}^2}$

• $\frac{\mathrm{\lambda }}{4 {\mathrm{\pi }}^2{\mathrm{\epsilon }}_0 {\mathrm{a}}^2}$

• $\frac{{\mathrm{\lambda }}^2}{2{\mathrm{\pi \epsilon }}_0\mathrm{a}}$

• $\frac{\mathrm{\lambda }}{2{\mathrm{\pi \epsilon }}_0\mathrm{a}}$

Two  changes  +q  and  -q  are  attached  to  the  two ends of  a  light rod of length L, as shown in figure. The system is given a velocity  ν  perpendicular to magnetic  field  $\overrightarrow{\mathrm{B}}$. The magnetic force on the system of  charges and magnitude of force on one charge by the rod, are respectively

• zero, zero

• zero, qvB

• 2qvB, 0

• 2qvB,  qvB

A charge q is uniformly distributed on a ring of radius r. A sphere of an equal radius is constructed with its centre lying on the periphery of the ring. The flux of electric field through the surface of the sphere will be

• $\frac{\mathrm{q}}{{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{2{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{3{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{4{\mathrm{\epsilon }}_0}$