The distance between a compression and a rarefaction in a sound wave is 5.4 m. Which of the following can be the wavelength of the wave?
a 1.2m b 2.7m c 3.0m d 3.4m
Which of the following best describes what happens if the split rings of a d.c motor are replaced by slip rings?
a the wire loop cannot turn at all
b the wire loop turns to a vertical position and stops turning eventually (ans)
c the wire loop turns clockwise and anti-clockwise repeatedly
d the wire loop turns 1 complete round and then stops
Wait!!! that's not the question i want to ask for the 2nd part. what i want to know now is what happens when slip rings of a.c circuit are replaced by split rings. ;p thanks and it would be good if someone could explain to me the real reason for why the wire loop turns to vertical position and stops turning eventually for the 2nd question. thank you
very interesting questions.
yup. ill reply for qn 2.
Slip ring commutators are used for AC generators.
Note: DC motors, use split ring commutators, as the commutators reverse the direction of the current every half revolution. Just use the right hand rule, or flemings left hand rule, to determine the direction of the torque and force.
eg.. >>>>>>>>> o--------------X >>>>>>>
"o " represents the wire, coming out of the page
"X" represents the wire going into the page
">>>>" is the magnetic field direction
"--------" will be the armature of the motor
so if u see the above diagram, the armature will rotate in a clockwise direction, use RH rule(suppose that current is flowing through and its a DC motor), at that position above, the torque is at maximum, and force on the wire is also maximum.
T=BIAnCos(@).... @ represents tither
and force experienced on a wire in a mag field: motor effect
F=BILSin(@)
.
Now, as you were saying, if a slip ring was used instead, it means that the commutator will NOT be able to reverse the currents. what will happen will be a standstill where the armature is at perpendicular to the magnetic field, or as u say, vertical.
why? Cause the force and torque on both of the wires are equal (Use the hand rule to determine), therefore, they cancel each other out.
Resultant force = 0. no movement
For 1:
A. Since they didn't say that the compression and rarefaction was next to each other, the length given would be 2/(2n+1) * 5.4, where n = 1, 2, 3...
In this case, n is 4.