Select the best answer: 1. Doubling the number of turns it has while leaving eve
ID: 2155413 • Letter: S
Question
Select the best answer:1. Doubling the number of turns it has while leaving everything else unchanged physically alters a solenoid self-inductance by.
a. stay the same
b. double
c. halved
d. four times greater
2. A small light bulb is in series with an air-core coil and an ac power supply such that the lamp glows brightly. An iron core is the inserted into the coil, and the lamp
a. grows brighter
b. goes out completely
c. grows dimmer
d. is unaffected
3. The magnetic force on a wire carrying a current is
a. Independent of the relative directions of the field and current.
b. perpendicular to the direction of the current flow and the direction of the magnetic field
c. perpendicular to the current flow and parallel to the magnetic field
d. parallel to the current flow and perpendicular to the magnetic field
4. When a charge particle moving in a magnetic field traveling so that its velocity vector is perpendicular to B, its path will be
a. an ellipse
b. a parabola
c. a circle
d. a logarithmic spiral
5. A coil of wire is connected to a galvanometer, when a bar magnet is moved in and out of the coil, the galvanometer read a current. The current results because
a. The coils acts like a transformer
b. The changing magnetic field induces an electric field in a wire
c. An electromagnetic wave is generated
d. The wire is ferromagnetic
6. Electromagnetic Induction is used in the operation of
a. Generator
b. Transformer
c. Motor
d. All of the above
7. A current can be made to flow in a coil of wire if
a. it is connected to a battery
b. it is put into motion near a magnet
c. A magnet is put into motion near it.
d. All of the above
Questions:
(Example for the form of answer for the 1st & 2nd question: Second Newton Law: F = ma where F-Force in Newton, m-mass in kilogram and a-acceleration in m/s2).
1. Write the formula for the Ampere
Explanation / Answer
1. D 2.C 3. B 4.C 5.B 6.D 7.D 1.Dude i cudn't understand how to write the integrals and other so i'm attaching the link so that u can refer there http://en.wikipedia.org/wiki/Ampere%27s_law http://www.pa.msu.edu/courses/1997spring/phy232/lectures/ampereslaw/ampere.html 2.Dude i cudn't understand how to write the integrals and other so i'm attaching the link so that u can refer there http://www.citycollegiate.com/xii_chpxiv6.htm 3.An electric motor is a rotating machine which converts an electrical input power into a mechanical power output. A generator converts a mechanical power input into an electrical power output. Since one process is the converse of the other, a motor may be made to operate as a generator, and vice versa. This duality of function is not confi ned to d.c. machines. An alternator can be made to operate as a synchronous a.c. motor, and vice versa. To demonstrate the conversion process involved, let us reconsider two simple cases that were met when dealing with electromagnetic induction.Consider a conductor being moved at constant velocity, through a magnetic fi eld of density B tesla, by some externally applied force F newton. Work done in moving the conductor, W = Fd newton metre mechanical power input, P1=W/t watt so, P1 =(Fd)/t watt and since d /t is the velocity, v at which the conductor is moved, then P1 = Fv watt. . . . . . . . . . . . .[1] However, when the conductor is moved, an emf will be induced into it. Provided that the conductor forms part of a closed circuit, then the resulting current fl ow will be as shown in Fig. 7.2 . This induced current, i, produces its own magnetic fi eld, which reacts with the main fi eld, producing a reaction force, Fr , in direct opposition to the applied force, F . Now, Fr = Bil newton Assuming no frictional or other losses, then the applied force has only to overcome the reaction force, such that: F=Fr = Bil newton so eqn [1] becomes P1=Bilv watt. . . . . . . . . . . .[2] Also, induced emf,e=Blv volt so generated power,P2=ei watt....[3] therefore, P2= Biv watt. . . . . . . . . . . .[3] Since [3] = [2], then the electrical power generated is equal to the mechanical power input (assuming no losses). Now consider the conductor returned to its original starting position. Let an external source of emf, e volt pass a current of i ampere through the conductor. Provided that the direction of this current is opposite ,then the conductor will experience a force that will propel it across the fi eld. In this case, the same basic arrangement exhibits the motor effect, since the electrical input power is converted into mechanical power. Although the above examples involve linear movement of the conductor, exactly the same principles apply to a rotating machine. 4.They interact according to the equation Force = i * L X B. OR: where i--->current F = iLB when they are parallel. Each wire (or moving charge) has a magnetic field associated with it. These magnetic fields interact between the wires creating increased (or decreased) magnetic field energy density. This results in the wires attracting or repelling each other.
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