# How do you determine the direction of velocity?

#### Caldus

URGENT: Magnet Stuff...

I have this quiz tommorrow on magnetism (not even sure if that's what it is, lol), but anyway, if someone could guide me with these problems (or at least one or something) below then I will greatly appreciate it!

There are four magnet diagrams that you need to draw the field and direction for:

1. First magnet is a north/south bar.
2. Second one is two south ends of a magnet close together.
3. Third is a wire with current.
4. Fourth is the wire but shown as if you were looking into the wire.

5. Find the force if there's 6 microcoulombs, 15 m/s, and 100 Teslas given.

(What I have so far for that one: First find the force, then at parallel which is just zero (the rule), and then at 30 degrees
F = qvBsin0. Am I right on this? What's the answer?)

6. There is a picture that shows a metal rod with wires looped around it. Label the north and south pole.

7. There are two magnets between a rod, maybe metal. The magnets poles are reversed on each side. You have some arrows showing magnetic field. The pole has a negative and positive end. You're suppose to draw an arrow for deflection...

(Right Hand Rule Stuff):

8. How do you determine the direction of force?

9. How do you determine the direction of velocity?

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#### drag

Re: URGENT: Magnet Stuff...

Greetings !
Originally posted by Caldus
There are four magnet diagrams that you need to draw
the field and direction for:

1. First magnet is a north/south bar.
2. Second one is two south ends of a magnet close together.
3. Third is a wire with current.
4. Fourth is the wire but shown as if you were looking
into the wire.
1. Magnetic field lines go from north to south pole.
2. Magnetic field lines do not intersect and since
they're going in the same direction they do not
connect. They just "circle back" towards their
north poles and you can see from their form
that the two poles repel each other.
3. According to the left-hand rule (curve your fingers
to see the circuilar field and your thumb shows the current).
4. The same (the field lines' around the wire).
Originally posted by Caldus
5. Find the force if there's 6 microcoulombs, 15 m/s,
and 100 Teslas given.

(What I have so far for that one: First find the force, then at parallel which is just zero (the rule), and then at 30 degrees
F = qvBsin0. Am I right on this? What's the answer?)
I think you are. (Answer: F = qvBsin30 = 4.5 * 10^-3 N)
This is right-hand rule stuff.
Originally posted by Caldus
6. There is a picture that shows a metal rod with wires
looped around it. Label the north and south pole.
It depends on the direction of the current
flow through the loop. Basicly you have a magnetic
field within the rode from each loop and that occumulates
into the total field of the rod that is what you're
asked to discribe. Outside the rod the field lines
go from north to south pole as a normal magnet.
(You can use the left-hand rule and follow the first
loop to see where the field is pointed inside the coil.)
Originally posted by Caldus
7. There are two magnets between a rod, maybe metal. The magnets poles are reversed on each side. You have some arrows showing magnetic field. The pole has a negative and positive end. You're suppose to draw an arrow for deflection...
I don't understand what you mean in this one.
Originally posted by Caldus
(Right Hand Rule Stuff):

8. How do you determine the direction of force?

9. How do you determine the direction of velocity?
According to the rule.
You fingers (streight hand) are the velocity of
the charge, the magnetic field lines enter your
open palm and exit on the other side and the
thumb (perpendicuilar to the other fingers
in the 3rd plane) is the force. The force
on an electric charge in a magnetic field is
thus always perpenduilar to the velocity of
the charge.

Live long and prosper.

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