# Magnetic Compass

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#### Students’ Learning Outcomes

·         Explain the Earth’s magnetic field and relate it with the use of a magnetic compass.
·         Make a magnetic compass and show its working.

#### Information for Teachers

·         Earth behaves like a very large bar magnet with a north pole and a south pole.
·         The Earth has its own magnetic field. The Rather magnetic field is strongest at the poles.
·         If a bar magnet is suspended freely, it always stays in N-S direction.
·         Magnetic compass contains a magnetic needle that can spin freely, but always rests in north-south direction.
·         As the needle of the compass points towards north of the Earth, we can find the other direction too.

#### Material / Resources

Bar magnets, iron needles, iron filings, small pieces of aluminum foils, plastic bowl, markers, water, laboratory compass, textbook.

#### Worm up Activity

·         Show a magnetic compass to the students and ask the following questions:
—-What is in my hand?
—–What are its uses?
·         Tell the students that it is magnetic compass.
·         Give the compass to the students and ask them to pass it on. Ask everyone to observe it carefully.
·         Ask them: In which direction are the ends of the compass needle?
·         Say them to change the direction of the ends of compass needle and see where they stay again.
·         Ask the students: Why the compass needle always stays in north- south direction. What do you think may be uses of this compass?
·         Announce today’s topic and tell them that they will make a magnetic compass using the easily available materials.

#### Activity 1

·         Call two students and give them a thread and two bar magnets.
·         Ask them to put one bar magnet on the table.
·         Then direct them to suspend the other bar magnet from a stand or any support with the help of thread over the magnet placed on the table.
·         Say them to disturb the suspended magnet and observe its directions when it comes to rest.
·         Ask them: What is the direction of the suspended magnet?

(Expected response:  Its north pole is towards the south pole of the magnet on the table and south pole is towards the north pole of the magnet below it).
·         Ask them: Why is it so?
(Expected response:  Because opposite poles attract each other).
·         Ask them to disturb the suspended magnet again and observe its directions when it comes to rest.
·         Ask them: Does the position of the suspended magnet change?
(Expected response:  No, the direction of freely suspended magnet depends upon the direction of the magnet over which it is suspended).
·         Ask them:  what other inference they can draw from it?
(Expected response:  the suspended magnet stays in particular direction because of some other magnet).
·         Now ask them to remove the magnet from below and disturb the directions of the suspended magnet.
·         Ask them: Where does it come to rest?
(Expected response: In N-S direction)
·         Ask them: Why is it so?
·         After their response, inform them that it seems that a huge magnet is lying inside the Earth along N-S direction. This Earth magnet forces the suspended magnet to stop along its direction. So we can say that the Earth behaves like a magnet and it has two poles.

#### Activity 2

·         Divide the students into groups and give each group a sewing needle and a bar magnet.
·         Ask them to place the sewing needle on the table and rub it with north or south pole of the bar magnet for 15-20 times.
·         Direct them to bring the needle near the steel pins and check whether it has been magnetized?
(Expected response: Yes it has become a magnet).
·         Ask them to identify the north and south poles of the needle by bringing the north pole of a magnet near the ends of the needle.
·         Tell the students that if it is repelled then this end of needle is north pole and the other end is south pole.

·         Ask them to paint the north pole red and south pole is blue.
·         Ask them to place the needle on a slice of a cork or on a piece of thermos pore.
·         Ask them to fill water in a small bowl and place the cork with needle in it.
·         Ask them to observe in which direction does the needle stay?  Tell them it always stay along N-S direction.
·         Now guide them that compass needle is also a needle-like magnet that is pivoted at its center so that it can rotate freely. A circular scale is provided around the needle on which north, south, east and west are indicated as four directions. Compass needle always stays along N-S direction.

Sum up / Conclusion

·         The Earth behaves like a magnet. It has its own magnet field.
·         The magnet compass is a tiny magnet. Its needle is pivoted at center to rotate freely.
·         The compass needle always stays in N-S direction. It can be used to locate the direction at any place. It is also used to locate the direction of Qibla.

#### Assessment

·         Divide the students into groups.
·         Provide a sewing needle to each student and a bar magnet to each group.
·         Ask them to follow all the steps in the above activity.
·         Appreciate the students who finish the task successfully.
·         After the activity, ask the following questions:
1.       Does the Earth has poles?
2.       How many poles does the Earth have?
3.       Why does compass needle always stay in a particular direction?
4.       What is the pole of the Earth under the compass needle if it pointing towards north?
5.       What are the uses of magnet compass?
6.       How can the direction of Qibla be known by a compass?