1. Unit 4 Day 7: Magnetic Fields due to Wires Magnetic Field in a Straight Wire Magnetic Fields in 2 Parallel Conducting Wires, Side by Side Magnetic Forces Between Parallel Wires

2. Magnetic Field in a Straight Wire In a straight, current carrying conductor, there exists a magnetic field around the wire, proportional to the current r is the radial distance from the conductor

3. Two Current Carrying Conductors Side by Side If there are two current carrying conductors side by side, but the current is going in the opposite directions, then the total magnetic field will have a magnitude of:

4. Magnetic Force Between Parallel Wires We know that when a current carrying conductor is in the presence of a magnetic field, it feels a force exerted by that field.

5. Magnetic Force Between Parallel Wires The force that wire #2 sees is due to the magnetic field generated by wire #1, separated by distance d Similarly, wire #1 sees a force due to the magnetic field of wire #2 (Newton’s 3 rd Law)

6. Magnetic Forces Between Parallel Wires Parallel currents in the same direction exert an attractive magnetic force on each other Parallel currents in the opposite direction exert a repulsive force on each other It can be shown from Newton’s 3 rd Law, that the magnetic force produced by I 2 exerts an equal but opposite force on I 1