two llong parallel vertical wires 0.3m apart are placed east-west of one another.The current in the eastely one is 30A and that in the other is 20A.Both currents flow upwards.The earth"smagnetic field is horizontal directed north and has magnetude field B=20x10^-6T.Calculate the resultant force per meter on each wire

The external magnetic field exerts a force on each wire that equals I x B per meter. The direction would be west.

Parallel wires also exert a force on each other. It is an attractive force when the currents are in the same direction. You can find the formula at
http://theory.uwinnipeg.ca/physics/mag/node10.html

Add it vectorially to the force caused by the external B field.

To calculate the resultant force per meter on each wire, we need to find the magnetic force on each wire and then divide it by the length of the wire.

The magnetic force on a wire can be calculated using the formula:

F = B * I * L * sinθ

Where:
- F is the magnetic force
- B is the magnetic field strength
- I is the current flowing through the wire
- L is the length of the wire
- θ is the angle between the current direction and the magnetic field direction

In this case, both wires are parallel to each other and the magnetic field is horizontal and directed north. Since both currents flow upwards, the angle θ between the current direction and the magnetic field direction is 90 degrees.

For the wire with a current of 30A:
F1 = B * I1 * L * sinθ
= (20x10^-6 T) * (30 A) * (L) * sin(90°)
= 0.0006 N * L

For the wire with a current of 20A:
F2 = B * I2 * L * sinθ
= (20x10^-6 T) * (20 A) * (L) * sin(90°)
= 0.0004 N * L

Now we can divide these forces by the length of the wire (which is 1 meter):
Resultant force per meter on each wire = F / L
F1/L = 0.0006 N
F2/L = 0.0004 N

Therefore, the resultant force per meter on each wire is 0.0006 N for the wire with a current of 30A and 0.0004 N for the wire with a current of 20A.