Magnetic effect of electric current
A wire carry current generate magnetic field around itself. to understand its effect you can do a small activity. Take one cell or a battery of around 9V, a piece of conducting wire, find a magnetic compass .
connect the wire with the battery and bring the magnetic compass close to the wire. you will find magnetic compass will deflect near to the wire. As you bring it closer to the wire deflection increases and when it's moved away from the wire deflection decreases.
it shows that hey the magnetic field decreases with the distance from the wire. Now if the position of wire and magnet are fixed I am current increases in the wire . then it is found that the deflection of compass increases with increase in current and vice versa. it means the magnetic field at any point around the wire depends on the current flowing in the wire.
Right hand thumb rule
Right hand thumb rule is used to find direction of magnetic field around the current carrying conductor. The magnetic field lines are circular around current carrying conductor. They form concentric circles. as we move away from the wire the distance between the magnetic field lines increases it means the field strength decreases with increase in distance from the wire. The magnetic field strength depends on the amount of current flowing in the conductor. if the flow of current increases the magnetic field lines become closer and stronger.
•consider you are holding a current carrying conductor in your right hand.
•Imagine that the direction of flow of current is in the direction of your thumb then then magnetic field will be in the direction of girl fingers.
•I have shown in the diagram below the wire is in blue colour the orange colour arrow represents the direction of flow of current.
•the green circle represents the magnetic field lines around the current carrying conductor. the direction of magnetic field at any point is tangent to the circle.
Magnetic field due to current carrying loop
When a straight wire is bent into the form of circle we get a simple loop. As we have already learned the current in the wire generates magnetic field. Now this straight wire is in the form of loop so magnetic field is stronger at the centre of the loop because all the field lines are concentrated in a very small region. The magnetic field outside of loop is weaker because field line are far from each other and spread in large area.
As shown in the image above magnetic field enters from one side in the loop and exits to other side from the loop. This situation is very similar to bar magnet. So a single loop of wire carrying current behaves similar to a piece of bar magnet. The loop has north and south pole like bar magnet. To find the magnetic poles formed by loops, use clock rule
What is a solenoid?
When large number of loops are stacked together, they form solenoid. The shape of solenoid is like spring. The solenoid is shown in the image below. Since each loop of solenoid contributes in the magnetic field. The magnetic field becomes strong inside the solenoid. Solenoids have many application as coil, inductor, etc.
If a soft iron core is inserted inside the solenoid it forms an electromagnet. The magnetic field of electromagnet is very strong because of the iron core. Roughly it becomes 1000 times stronger than the field of solenoid.
Note: Types of iron core also affects fields of electromagnet.
