Last time we saw that a current can create a magnetic field and a magnetic field causes a force on moving charge. We now have an equation to calculate the magnetic field from a long straight wire. We also can calculate the force between two parallel wires with a current flowing through them. Because force is a vector, we must consider the direction of the force. To do so, we must consider the directions of the two currents. We also need to recall that like magnetic fields repel, and opposite magnetic fields attract. If the currents move in the same direction, the magnetic fields between the wires are point in opposite directions, and thus we would have an attractive force. If the charges go in the opposite direction, the magnetic field in between the wires are in the same direction and repel each other. We have been focusing on how a current creates a magnetic field, it is also possible to do the opposite. When we look at induction, we focus on magnetic flux, which corresponds to the amount of magnetic field through an area. This helps us determine the magnetic field strength in a given location. It is important to ensure that the magnetic field is able to pass through the area, and not parallel through it. According to Faraday's Law, a changing magnetic flux can create an emf. To determine the direction of the induced current we need to consider Lenz's Law. Lenz's Law states that the induced current flows in such a way to counteract the change in magnetic flux. What this means is that if the magnetic flux is increasing, the induced current will generate a magnetic field that points in the opposite direction. In the case where the magnetic flux is decreasing, the induced current will increase the magnetic flux.