Can someone explain why these are the answers? A loop of wire 5 cm in diameter i
ID: 2078202 • Letter: C
Question
Can someone explain why these are the answers?
A loop of wire 5 cm in diameter is hung by cloth thread, and arranged so that it can swing between the poles of an electromagnet as shown in the figure. The plan is that the plane in which the loop swings will be parallel to the plane of the coils that make up the magnet. In the drawing those coils are above and below the plane of this paper. The coil is released from some height h. The magnetic field which is 0.3 T, is confined to the region between the electromagnets, so that at the original time when the loop is released it is experiencing no field, and remains so until it enters the region between the magnets. Where there is a field, it is spatially uniform. When the ring enters the magnetic field (A) it will speed up (B) it will slow down (C) it is unaffected since it is not in a circuit (D) it will bounce back Which is true? (A) There will be a clockwise current induced in the loop when it enters the magnetic field (B)There will be a counter-clockwise current induced in the loop when it enters the magnetic field (C) No current is induced in the loop (D) There will be a clockwise current induced in the loop first when it enters the field, that then reverses as the loop begins to rise (B)There will be a that then reverses as the loop begins to rise counterclockwise current induced in the loop when it enters the field, that then reverses as the loop begins to rise If the loop twists as it descends so that it is no longer going straight across the face of the electromagnet, (making it look more elliptical as we see it) what happens to the flux through the loop? (A) It increases because the angle changes. (B) It decreases because the field changes (C) It increases because the area changes (D) It decreases because the angle changes (E) It stays constant. Which is true as the loop swings into the region of the field? (A) A current is induced in the wire that creates a field pointed out of the page (B) A current is induced in the wire that creates a field pointed into the page (C) A current is induced in the wire that creates a field pointed to the right (D) A current is induced in the wire that creates field pointed to the left (E) No current is induced in the field. Suppose I were to reverse the polarity of the electromagnet just as the coil enters the field. After the polarity is reversed, (A) the coil will reverse its direction (B) the coil will speed up (C) the coil will behave just as it did before the polarity was reversed (D) the coil will immediately stop. (E) the coil will flip over.Explanation / Answer
1. As per the Lenz's Law, the induced current in the coil is such that it opposes the cause that has created it. Therefore it will slow down the movement of coil Answer (B)
2. Again as per Lenz's Law, Since when coil is entering the magnetic field, Inward Magnetic Flux is increasing, hence it will create its own magnetic field which should be outward, which is possible by counter clockwise current. Answer (B)
3. Due to twisting of loop, angle between Area vector and Magnetic Field changes, hence magnetic Flux decreases Answer (D)
4. As seen in previous question No. 2., the anticlockwise current gets induced in the coil, which can produce magnetic Field outwards. Hence Answer is (A)
5. Changing polarity doesn't affect the movement of coil. Since as per Lenz's law, it should oppose the cause. The cause here is motion of coil, hence it should be slowed down as before. Hence Answer is (C)