- We already know that electric current produces a heating effect.
- similarly it also produces magnetic effect
The term magnetic effect of electric current means that an electric current flowing through a wire produces a magnetic field around it
This means electric current can produce magnetism
- Take a one meter long insulated copper wire. wind it on a large iron nail. connect the two ends of the wire to a battery
- keep some tiny iron nails near the large iron nail.
- you will see the large iron nail attracts the small iron pieces.
- This means the large iron nail gets magnetized and attract the iron pieces.
- As the battery is removed iron nails gets detached from the large iron nail.
What is a Magnet-
- Magnet is an object which attracts pieces of iron, steel,nickel cobalt etc.
- It is found that the magnet has two poles North and south pole
- Like poles repels each other while unlike poles attract each other
- Just as an electric charge creates an electric field around it. similarly an magnetic field creates a magnetic field around it.
- Basically magnetic field means the area of influence of the magnet,up-to where its force is exerted.
- The region around a magnet where its force of attraction or repulsion can be detected is called magnetic field.
- The magnetic field has both magnitude and direction.
What is Magnetic field lines
- The magnetic field lines are the lines drawn in a magnetic field along which a north magnetic pole would move.
- Magnetic field lines always begin from north pole and ends at south pole.
How magnetic field lines look.
Can we see magnetic field lines?
Yes we can plot magnetic field lines to see how it looks.
1.To plot magnetic field lines using a bar magnet
- Place a card thick paper over a strong bar magnet
- sprinkle a thin layer of iron fillings over the magnet. gently
- You will observe that the iron fillings arrange themselves in a regular pattern.
- The arrangement of iron fillings gives us a rough picture of how magnetic field lines look.
Have a look at this Small video to see how to perform this activity.
To Plot the magnetic field lines using a bar magnet by using a compass
What you’ll need:
- A bar magnet
- A piece of white paper
- A pencil or pen
- A compass
What you’ll do:
- Place the bar magnet in the middle of the paper. Trace the outline of the magnet – that way you can put it back in the exact same spot if it gets bumped.
- Place the compass at one pole of the magnet and make a dot next to it showing the direction the compass arrow points.
- Move the compass so that the base of the arrow is at the dot you’ve just made. Now make a new mark where the tip of the arrow is pointing this time.
- Keep doing this until you reach the other end of the magnet.
- Connect the dots. You’ve just drawn one magnetic field line!
- Go back and begin again, starting at a different spot than you did the first time. Repeat the above steps.
- Repeat the process until you have drawn as many lines as you can for both ends of the magnet. You will now have an accurate representation of magnetic field lines.
- Different magnets will give you different field lines. Try repeating these steps with magnets of different sizes and shapes.
Here Is another Video performing this activity for you
From the above two activity it is concluded that
- The Magnetic field lines leave the north pole of a magnet and enter the south pole
- The strength of the magnetic field is indicated by the degree of closeness of the field lines .
- where the field lines are closet together ,the magnetic field lines are strongest
- The magnetic field lines don’t intersect/cross each other.
Magnetic field of earth
- A freely Suspended Magnet always points in the North-South direction even in the absence of any other magnet.
Before discussing why let us know our mother earth a bit clearly.
- You Know that Earth has two poles. North pole and south pole. The poles you have heard about before is actually the Geographical north and south pole.
Lets see this image
- This image is showing earths Geographical north and and south pole.
- Now there is another pair of poles which is called magnetic poles of the earth.
- The magnetic pole of the earth is actually in opposite of the geographical pole of the earth.
- This means The South magnetic pole is in the direction of geographical north pole and north magnetic pole is in south of geographical pole.
Another Image from Google Search to explain you better
See this image
- When we use a compass it always showed in the north south direction which suggests the north pole of the compass is attracted to the south of pole of the earth magnetic field and similarly the south of the magnetic compass is directed towards the north pole of the geographical magnet.
- This is the reason magnetic compass show as actual geographical north and south direction.
Remember The axis of earth’s magnetic field is inclined at an angle of about 15 degree with the geographical axis of the earth.
So it is concluded that earth is an imaginary huge magnet which is pointing in the opposite of the geographical poles.
It is believed that the earths magnetic field is due to the magnetic effect of current flowing in the liquid core of the center of the earth.Thus our earth is huge Electro Magnet.
Questions Asked From This Topic in CBSE
- What is meant by the term, “magnetic field”?
- Why does a compass needle show deflection when brought near a bar magnet? (AI 2008)
Ans. Compass needle is itself made up of tiny magnet. When it is brought near a bar magnet, its magnetic field lines interact with that of the bar magnet. Hence needle shows defection
- Draw a diagram to show the magnetic field lines around a bar magnet. List any two
properties of magnetic field lines. (AI 2008)
Visit Here For The Second part Of This Lesson