Final answer:
The direction of the magnetic field at a point above a current-carrying wire can be determined using the right-hand rule. For multiple wires, the total magnetic field is the vector sum of the fields from each wire. The magnetic field strength from a single wire is given by the formula involving the permeability of free space, the current, and the distance from the wire.
Step-by-step explanation:
To determine the direction of the magnetic field at point P, which is 5 cm above a current-carrying wire, we must use the right-hand rule. Imagine holding the wire with your right hand so that your thumb points in the direction of the current.
Then, your fingers will curl in the direction of the magnetic field lines. If the current is going into the page (as viewed from above), the magnetic field at point P, above the wire, will be directed to the left. If the current is coming out of the page, the magnetic field at point P will be directed to the right.
In tasks involving multiple wires with current, such as calculating the magnetic field strength at a point near three parallel wires carrying identical currents, the superposition principle applies.
This principle states that the total magnetic field at a point is the vector sum of the magnetic fields due to each wire individually.
For example, if we're asked to find the magnetic field at a point due to a long straight wire with a given current, we would use the formula B = (μ0 * I) / (2π * R), where B is the magnetic field, μ0 is the permeability of free space, I is the current in the wire, and R is the distance from the wire to the point of interest.