Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
24 Cards in this Set
- Front
- Back
- 3rd side (hint)
|
where do magnetic fields point?
|
away from a north pole and toward a south pole
|
|
|
|
strength of magnetic field proportional to what?
|
number of lines per unit area that passes through a surface oriented perpendicular to the lines
|
|
|
|
when does a charge experience a magnetic force?
|
when moving perpendicularly to a magnetic field
|
|
|
|
what velocity component gives rise to a magnetic force?
|
v sin theta
|
|
|
|
a magnetic force is ____ to the velocity and magnetic field
|
perpendicular
|
|
|
|
If a moving charge is negative instead of positive, will it follow the right hand rule?
|
no, it'll go in the opposite way
|
|
|
|
equation of magnetic field and unit
|
B=F/(charge)(v sin theta)
F is magnetide magnetic force, charge is magnitude of test charge, v is magnitude of velocity. This is a vector. Angle is Tesla, newton*second/coulomb*meter. |
|
|
|
Tesla
|
newton*second/Coulomb*meter
|
|
|
|
equation for centripetal force
|
F_c=mv^2/r
|
|
|
|
a radius of a circle is ___ proportional to magnitude of magnetic field. what is the equation that shows this?
|
inversely. r=mv/qB
|
|
|
|
magnetic force on a current-carrying wire of length L, plus explanations and equivalents for each variable.
|
F=ILB sin theta
F=(deltaq/deltat)(vdeltat)B sin theta d.q/d.t=I, v*dt=L |
|
|
|
Whenever a current in a wire reverses, direction, what happens to the force?
|
also reverses direction
|
|
|
|
how to find length of a wire given diameter and # turns of wire
|
#turns*pi*diameter drum of wire
|
|
|
|
Example 5, p. 21.5
The voice coil of a speaker has a diameter of 0.025 m, contains 55 turns of wire, and is placed in a 0.1 T magnetic field. Current in the voice coil is 2.0 A. a)determine B that acts on coil and cone. b)voice coil and cone have combined mass of 0.020 kg. Find acceleration. |
force=.86 N, acceleration=43 m/s^2
|
Use equation F=ILB sin theta for magnetic force on a wire. Use (number of turns of wire*pi*diameter of cone/wire) to find length. assume theta is 90 because the wire will be going straight up and down. for acceleration, simply use a=F/m, using answer from number one and the mass of the coil and cone to get the answer.
|
|
|
21.14
The solar wind is a thin, hot gas given off by the sun. Charged particles in this gas enter the magnetic field of the earth and can experience a magnetic force. Suppose a charged particle traveling with a speed of 8.82E+6 m/s encounters the earth's magnetic field at an altitude where the field has a magnitude of 1.18E-7 T. Assuming that the particle's velocity is perpendicular to the magnetic field, calculate the radius of the circular path on which the particle would move if it were an electron. |
426 m
|
v and B are given. m=9.11E-31 kg=mass of electron. c=1.6E-19 C, charge of electron.
Equation= r=mv/eB |
|
|
21.24
An electron has a kinetic energy of 1.91E-17 J. It moves on a circular path that is perpendicular to a uniform magnetic field of magnitude 5.10E-5 T. Determine the radius of the path. |
7.23×10-1 m
|
1.use KE=1/2mv^2 to find v
2.plug it into r=(mv)/qB =answer m_electron=9.11E-31 kg |
|
|
21.31
A wire carries a current of 0.618 A. This wire makes an angle of 58.0° with respect to a magnetic field of magnitude 4.63E-5 T. The wire experiences a magnetic force of magnitude 7.41E-5 N. What is the length of the wire? |
3.05 m
|
use F=ILB sin theta. rearrange to L=F/IB sin theta. Everything is given. (see pg. 657 if questions)
|
|
|
21.39
A 0.502 m length of wire is formed into a single-turn, square loop in which there is a current of 14.5 A. The loop is placed in a magnetic field of 0.137 T, as shown in the drawing below. What is maximum torque? |
.0313 N *m
|
torque=NIABsin theta
get rid of N, doesn't matter. 1.to find area, take L/4=one side. square that for area 2.everything else is given see page 661 for questions |
|
|
21.46
What must be the radius of a circular loop of wire so the magnetic field at its center is 1.66E-4 T when the loop carries a current of 12.1 A? |
.04579 m
|
1.Start with B=(u_0)(I)/2R
2.rearrange to solve for R u_0=4piE-7 T*m/a |
|
|
21.47
A long, straight wire carries a current of 48.5 A. The magnetic field produced by this current at a certain point is 7.73E-5 T. How far is the point from the wire? |
.125 m
|
Use B=(u_0)(I)/2piR
u_0=4piE-7 Tm/A this is for straight wire |
|
|
equation to use for circle of wire, straight wire, for whatever
|
circle
B=uI/2R straight b=uI/2piR |
|
|
|
21.50
A +6.06 μC charge is moving with a speed of 7.62E+4 m/s parallel to a very long, straight wire. The wire is 4.80 cm from the charge and carries a current of 68.4 A in a direction opposite to that of the moving charge. Calculate the magnitude of the force on the charge. |
1.316E-4 N
|
1.use this equation:
F=QVBsin theta 2.substitute B=uI/2pir for B |
|
|
21.67
The maximum torque experienced by a coil in a 0.738 T magnetic field is 8.53E-4 N·m. The coil is circular and consists of only one turn. The current in the coil is 3.51 A. What is the length of the wire from which the coil is made? |
6.43×10-2 m
|
1.Torque=NIAB sin theta. Solve for A. Everything is given.
2.pir^2=area. solve for r. 3.circumference=2piR=answer |
|
|
21.52
A very long, straight wire carries a current of 0.195 A. This wire is tangent to a single-turn, circular wire loop that also carries a current. The directions of the currents are such that the net magnetic field at the center of the loop is zero. Both wires are insulated and have diameters that can be neglected. How much current is there in the loop? |
6.21×10-2 A
|
set it up as a ratio between magnetic field of a straight wire=magnetic field circle loop. Cancel shit out, you'll find that I_1/pi=I_2. That's the answer.
equation for straight wire B=uI/2piR loop B=ui/2R |
