Show all work. Draw diagrams and explain answers as needed. 3) The north pole of
ID: 1302402 • Letter: S
Question
Show all work. Draw diagrams and explain answers as needed.
3) The north pole of a bar magnet is held near a compact coil with 1000 turns of wire as shown below. Note that the field lines extend through the coil and magnetic field lines point outward from north poles (by convention) a) The magnet is pushed so that it moves rapidly to the right, toward the coil. To an observer looking into the coil from the other side, will the induced current circulate clockwise or counterclockwise? Explain how you know. Repeat for motion of the magnet away from the coil b) The coil has a radius of 1 cm and the field is uniform across its cross-section. If over a 2 ms interval during which the magnet is moved towards the coil the field magnitude across the cross-section rises by 0.07 T, what EMF is developed in the coil?Explanation / Answer
a) Since the magnetic flux is increasing when the magnet is moved near to the coil, So, the direction of induced current will be such that it will tend to minimize the change, SO, the direction of current as observed by the observer will be in CLOCKWISE DIRECTION. Then only it will induce a magnetic field of its own in the direction opposite to that of magnet.
When the magnet moves away from coil, the induced current will be in the direction will induce a magnetic field in the direction as of the magnet. SO , the direction of current as observed by the observer will be in COUNTERCLOCKWISE DIRECTION.
b) delta B / delta t = 0.07/2 * 0.001 = 35
Area of coil = pie * r2 = 3.14 * 0.0001 = 3.14 * 10-4
Emf induced = - N A dB/dt = - 1000 * 3.14 * 10-4 * 35 = -10.99 V
The negative sign shows the polarity of the emf induced while its magnitude is 10.99 V or 11 V.