# Homework Help: I NEED IMMEDIATE HELP for solving the magnitude and direction of current

1. Mar 26, 2007

### Bk8907

ok here's the prob.

Two parallel wires are 20cm apart. EAch wire is 1.5 m long. The wire on the left carries 10 A of current up. Find the magnitude and direction of the current of the wire on the right ir it is REPELLED WITH A FORCE OF 10N.

2. Mar 26, 2007

### .ultimate

Appy Felmmings left hand rule

3. Mar 26, 2007

### Bk8907

LEFT hand? I thought there was only RIGHT hand

4. Mar 26, 2007

### Ki Man

Last edited: Mar 26, 2007
5. Mar 26, 2007

### .ultimate

Strech Left hand's First finger, forefinger n thumb

First Finger - direction of magnetic field
Middle Finger - Direction of current
Thumb - direction of force on the conductor/wire

Right hand is for Electromagnetic Induction EMI

Magnitude can be calculated by F=B.I.L (or BqV in case or a moving charged partile)

6. Mar 26, 2007

### Bk8907

what? wrong section?

7. Mar 26, 2007

### NeoDevin

Questions like this belong in the homework help section.

8. Mar 26, 2007

### Bk8907

ok, so from my problem, the current on the second wire is up (north) and what does B stand for again?

9. Mar 26, 2007

### Bk8907

oh ok neo devin

10. Mar 26, 2007

### .ultimate

Addendum - Apply Right hand thumb rule to find direction of magnetic field around the wire carrying current where thumb is for direction of current and curled fingers are for magnetic filed( this is different from motor and dyanmo rule)

11. Mar 26, 2007

### Bk8907

so the current on the second wire IS north, but now with the 10N repulsion, how do i find magnitude?

12. Mar 26, 2007

### .ultimate

B is magnitude of the magnetic filed

B= $$\frac {u_0.I}{2 \pi r}$$

$$u_0$$ permeability of vacuum

(Dont have enough knowledge to assist in this context, sorry)

13. Mar 26, 2007

### Bk8907

wow what a formula! i use F=2K'I/r