Can You Help Review My Physics Assignments for Engineering College Prep?

[physicslady]

Hi! Iam trying to get back to studying after several years of working, and currently Iam trying to higher my grades so I can make it to engineering college.. I would be grateful if you guys could help me with these assignments and check if I have done it right, because I really want an A.

ASSIGNMENT 1
1. Homework Statement
Currents are equal in the two long straight parallel conductor but flowing in the opposite directions. The distance between the conductors is 10 cm. Magnetic field size at a point midway between the leaders is 80 microT, apart from the Earth's magnetic field.

a, How big is the current in the conductors?
b, Calculate the force on every meter of one of the conductors

Homework Equations

a, B=k*I/a
b, F=B*I*l

3. The Attempt at a Solution
a=10cm
B=80*10^-6 T
l=?
k=8,99*10^9
I=(B/k)*a

l=1m
B=80*10^-6 T
I=from a
F=(80*10^-6)*1*I(from a)

ASSIGNMENT 2
When a negatively charged particle is moved from the bottom plate to the top plate in a homogenous electric field 2,9*10^-8 J is being transformed to potential energy. Is the top or the bottom plate positively charged? How big is the charge of the particle? Current between the plates is 100V.

W=q*U --> q=W/U

q=2,9*10^-8/100V=2,9*10^-10 top is positive and bottom is negative. (I am not sure about this)...ASSIGNMENT 3
A electron passes through a vertical magnetic field like the figure shows. The path is in a horisontal plane.
a, Give the motion direction in the path.
b, The electrons velocity is constant under the whole passage through the field, explain this!

No equations

My exp;
a, The force will point to the "middle" of the circular motion that occurs. The force is perpendicular to the motion, and the electrons motion is directed to the currents.

b, F is perpendicular to the motion, the velocity remains therefore constant because the electrons kinetic energy does not change.

ASSIGNMENT 4
Look at the figure, which force acts on a positive charged proton in the point P?

Equations:
F=k*(q1*q2)/r^2

Fres=F1+F2

Solution tried
F1=8,99*10^9*(1,602*10^-14)*(1,9*10^-9)/(0,03)^2

F2=8,99*10^9*(1,602*10^-14)*(6,2*10^-9)/(0,02)^2

Fres=? Iam not sure how to keep on going here...ASSIGNMENT 5
On which distance from a long straight conductor with the current 25 A, is the magnetic field=earth magnetic field, 47 microT?

Equations:
B=k*I/a

k=8,99*10^9
I=2,5 A
a=?
B=47*10^-6 T

Solution:
Solve for a.

Thank you a lot! As you see I've tried to solve most of it, would be grateful if anyone could go through them and see if anything is wrong, and tell me it so I can learn!

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[SteamKing]

physicslady:
Rather than dumping a bunch of problems in one thread, PF prefers that only one problem per thread be posted. Other members can reply without it getting confusing as to which question the reply is intended.

 

[Drakkith]

Hi physicslady,

Please start a new thread for each question, that way members can focus on each question in its own thread. In the meantime, thread locked.