Magnetic Effect of Current
In 1800s scientist Hans Oersted observe that, current flowing in a circuit effects the direction of needles of the compass. Picture, given below, shows his experiment. When the switch is closed current passes the circuit and direction of the magnet changes under the effect of magnetic field produced by current. Moreover, Faraday and Joseph Henry are other scientists showing the relation of magnetic field and current. If you move the magnet placed near the circuit you produce current or, if you change the current of circuit you can get current in another circuit placed near it. We will learn all the types of current produced by magnetic field.
Magnetic Field around a Wire
Current flowing in a linear wire produces magnetic field B=2k.i/d at a distance d. Here current measured in Ampere, distance measured in meter and k=10⁻⁷ N/Amps². Direction of the magnetic field produced around the wire is always tangential to the circle around the wire. We can find the direction of magnetic field by using right hand rule. As shown in the picture above, grab the wire with your four fingers, your thumb shows the direction of current and four fingers show the direction of magnetic field.
We show the current in two ways, if the current towards to us we show it with a dot, if the current is outward we show it with cross. Example: As shown in the figure given below, i₁ current produces 8N/Amps.m magnetic field at point K. Find the magnitude and direction of the total magnetic field produced by i₁ and i₂ at point L. Directions of the currents are shown in the picture below; Example: Two currents flow through the x and y axis of the wire. As you can see from the picture two points are located near the wires A and B. If the total magnetic field at A is BA, and total magnetic field at B is BB, find ratio of BA/BB? Magnetic field at point B;