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 :
$$40\,m/s$$
Solution :
The electron moves with constant velocity without deflection. Hence, force due to magnetic field is equal and opposite to force due to electric field.
Releted MCQ Question on Electrostatics and Magnetism >> Magnetic Effect of Current
Releted Question 1
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 battery is connected between two points $$A$$ and $$B$$ on the circumference of a uniform conducting ring of radius $$r$$ and resistance $$R.$$ One of the arcs $$AB$$ of the ring subtends an angle $$\theta $$ at the centre. The value of the magnetic induction at the centre due to the current in the ring is
A.
proportional to $$2\left( {{{180}^ \circ } - \theta } \right)$$
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