Home
Class 12
PHYSICS
A charged bead is capable of sliding fre...

A charged bead is capable of sliding freely through a string held vertically in tension. An electric field is applied parallel to the string so that the bead stays at rest of the middle of the string. If the electric field is switched off momentarily and switched on

A

the bead moves downwards and stops as soon as the field is switched on

B

the bead moved downwards when the field is switched off and moves upwards when the field is switched on

C

the bead moves downwards with constant acceleration till it reaches the bottom of the string

D

the bead moves downwards with constant velocity till it reaches the bottom of the string

Text Solution

Verified by Experts

The correct Answer is:
D
Promotional Banner

Similar Questions

Explore conceptually related problems

A charged bead is capable of sliding freely through a string held vertically in tension. An electric field is applied parallel to the string, so that the bead stays at rest at middle of the string. If the electric field is switched off momentarily and switched on

A beam of electron passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move

A ball of mass 1 g having a charge of 20 mu C is tied to one end of a string of length 0.9 m can rotate in a vertically plane in a uniform electric minimum horizontal velocity that must be given to the ball at the lowest position so that is complete the verticle circle is (let g= 10 ms^(-1))

Figure 6.20 shows a metal rod PQ resting on the smooth rails AB and positioned between the poles of a permanent magnet. The rails, the rod, and the magnetic field are in three mutual perpendicular directions. A galvanometer G connects the rails through a switch K. Length of the rod = 15 cm, B = 0.50 T, resistance of the closed loop containing the rod = 9.0 m Omega . Assume the field to be uniform. (a) Suppose K is open and the rod is moved with a speed of 12 cm s^(-1) in the direction shown. Give the polarity and magnitude of the induced emf. (b) Is there an excess charge built up at the ends of the rods when K is open? What if K is closed? (c) With K open and the rod moving uniformly, there is no net force on the electrons in the rod PQ even though they do experience magnetic force due to the motion of the rod. Explain. (d) What is the retarding force on the rod when K is closed? (e) How much power is required (by an external agent) to keep the rod moving at the same speed (=12 cm s^(-1) ) when K is closed? How much power is required when K is open? (f ) How much power is dissipated as heat in the closed circuit? What is the source of this power? (g) What is the induced emf in the moving rod if the magnetic field is parallel to the rails instead of being perpendicular?