Oersted found that current carrying conductor produced magnetic field around it. Now we will discuss about nature and magnitude of that magnetic field produced by conducting wire around it. Does this magnetic field depend on geometrical configuration of that conducting wire? We will resolve this question. To investigate this, we perform an experiment.
Insert copper wire perpendicular to the plane of that cardboard. Connect variable voltage supply to that cardboard with the help of key. Connect ammeter in series In the circuit.Fix a cardboard, it does not move. Sprinkle some iron pieces on that cardboard uniformly. Now ‘on’ the key and increase voltage. According to Ohm’s law, current is directly proportional to applied voltage. The increase in voltage led to increase in current at constant resistance.You can also use rheostat instead of variable voltage supply. The connections are as shown in figure
Observe the arrangement of iron pieces on the cardboard. Iron pieces re arranged in circular shape.The arrangements of iron pieces gives direction of magnetic field. From this experiment we conclude that
- Current carrying conductor produce magnetic field around it. Magnetic field lines are circular in shape and conducting wire act as a centre of circle.
- The circles near to conductor are dense as compared to circle having large radius. It means that magnetic field vary inversely to the distance.
- The current flowing conductor and magnetic field produced by it are lies in different plane.
- In fig ‘dot’ inside the circle indicates that current will going out from the plane of paper and ‘cross’ indicates that the current will going into the plane of paper.
- We also remember direction of current by arrow. When arrow moves toward you then you see the tip like dot. When arrow moves away from then you see the cross like structure of arrow.
- If we reverse the direction of current then direction of magnetic field also reverse.
- The direction of magnetic field gives by right hand thumb rule.
- The value of magnetic field is also depend on value of current flowing it.
- Magnitude of magnetic field due to long straight wire is
B = μ₀ I/ 2πR
Where,
μ₀ – absolute permeability.
I – current flowing in wire.
R- Distance from conducting wire.
Q) Explain the concept of magnetic field to current carrying conductor.