191. A circular loop of radius $$R,$$ carrying current $$I,$$ lies in $$x - y$$ plane with its centre at origin. The total magnetic flux through $$x - y$$ plane is
A
directly proportional to $$I$$
B
directly proportional to $$R$$
C
inversely proportional to $$R$$
D
zero
Answer :
zero
192. Two long straight parallel wires, carrying (adjustable) current $${I_1}$$ and $${I_2},$$ are kept at a distance $$d$$ apart, If the force $$'F'$$ between the two wires is taken as ‘positive’ when the wires repel each other and ‘negative’ when the wires attract each other, the graph showing the dependence of $$'F',$$ on the product $${I_1}\,{I_2},$$ would be :
A
B
C
D
Answer :
193. A beam of electrons is moving with constant velocity in a region having simultaneous perpendicular electric and magnetic fields of strength $$20\,V{m^{ - 1}}$$ and $$0.5\,T$$ respectively at right angles to the direction of motion of the electrons. Then the velocity of electrons must be
A
$$8\,m/s$$
B
$$20\,m/s$$
C
$$40\,m/s$$
D
$$\frac{1}{{40}}m/s$$
Answer :
$$40\,m/s$$
194. A conducting circular loop of radius $$r$$ carries a constant current $$i.$$ It is placed in a uniform magnetic field $${{\vec B}_0}$$ such that $${{\vec B}_0}$$ is perpendicular to the plane of the loop. The magnetic force acting on the loop is
A
$$ir\,{B_0}$$
B
$$2\pi \,ir\,{B_0}$$
C
zero
D
$$\pi \,ir\,{B_0}$$
Answer :
zero
