It is observed that a pencil sharpener gets attracted to both the poles of the magnet. Can you explain ?

The blade of a pencil sharpener is made of iron. Iron is a magnetic material. Since magnets can attract objects made of magnetic materials, a pencil sharpener gets attracted towards both poles of a magnet.

Chapter 1

Properties of a magnet: Attractive property. A magnet attracts magnetic substances like iron, steel, nickel, and cobalt. This property is used to separate iron from a mixture and also to remove iron filings from the eyes.

Directive property: A freely suspended magnet always aligns itself in the north-south direction. This property is used in the construction of a mariner's compass.

Chapter 2

Poles exist in pairs: If a magnet is broken into two parts from the middle, then each part is found to be a magnet.

Chapter 3

Magnetic property is maximum at the poles. It is found that the property to attract magnetic substances is more at poles.

If the magnet has no marking, then how will you find which end is North pole and which end is South Pole?

Finding directions using magnets.

Magnets have many properties which are useful to man. The most important property of magnets is their property of pointing towards the north and south directions. This distinguishing feature of magnets was first observed by the Chinese who used magnets to navigate through the seas.

The following activity demonstrates this property. Take a bar magnet and suspend it from a wooden stand using a thread. Now leave the magnet undisturbed until it reaches its rest position. Note down the direction in which the magnet points. Now rotate the magnet about one of its ends and leave it. Note down the position in which the magnet comes to rest. Repeat the process by rotating the magnet in different directions. It is found that the magnet comes to rest in the same position all the time. This direction is called the north-south direction.

Hence, using a magnetic compass and also observing the direction of the sun, it is possible to locate the north and south directions. The end of the magnet which points north is called the north pole, and the end which points south is called the south pole. This property of the magnet has been used in navigation since ages. Initially, people just used magnets suspended by threads for finding directions. Nowadays, a magnetic compass is used for the same purpose.

Magnets have many properties which are useful to man. The most important property of magnets is their property of pointing towards the north and south directions. This distinguishing feature of magnets was first observed by the Chinese who used magnets to navigate through the seas. The following activity demonstrates this property. Take a bar magnet and suspend it from a wooden stand using a thread. Now leave the magnet undisturbed until it reaches its rest position and note down the direction in which the magnet points. Now rotate the magnet about one of its ends and leave it. Note down the position in which the magnet comes to rest. Repeat the process by rotating the magnet in different directions. It is found that the magnet comes to rest in the same position all the time. This direction is called the north south direction. Hence using magnetic compass and also observing the direction of the sun, it is possible locate the north and south directions. The end of the magnet which points north is called the North Pole and the end which points south is called the South Pole. This property of the magnet has been used in navigation since ages. Initially, the people just used magnet suspended by threads. Nowadays, a magnetic compass is used for the same purpose.

Transcript

Predict and test which objects are made of magnetic materials and which are made of non-magnetic materials. Head to ngscence.com for a range of related resources for use in the classroom or at home. Non-contact Forces – Magnetic Force Place an iron nail on a table. Slowly move a magnet towards the nail. What do you notice? A magnet is an object with magnetic force. Magnetic force occurs in an object due to the motion of electrically-charged particles. As you observed when you moved the magnet near the iron nail, magnetic force can act at a distance. It is a non-contact force. It can act through solids, liquids and gases. Magnetic force can attract objects made of certain metals such as iron and nickel. Magnetic force cannot attract objects made of plastic, wood, rubber or glass. A magnet has two poles – a North pole and a South pole. It is at each pole that the magnetic force is the strongest. When the like poles of two magnets are brought together, they push or repel each other. When unlike poles are brought together, they pull or attract each other. Many objects make use of magnetic force. Some doors use magnets to keep them closed. Magnets are used to stick notes and photographs to refrigerators. They are used in electric motors, loudspeakers and can also be used for medical imaging and storing data on computer disks. When a magnet is hanging freely, it will come to rest with the South pole pointing in the direction of north and the North pole pointing in the direction of south. A compass is a device that uses this property to find the direction of north. A maglev (magnetic levitation) train has magnets that repel it from the track. This reduces friction and allows the train to travel at fast speeds.

Attraction and repulsion between magnets: Now place the two bar magnets on the toy cars such that the south pole of car A is followed by the south pole of car B in one scenario, and in another scenario, the north pole of car A is followed by the north pole of car B. Now bring car A near to car B. You will find that in the first scenario, car B moves away from car A, demonstrating repulsion. In the second scenario, where opposite poles are facing each other, car B attracts towards car A, showing attraction. Opposite poles of magnets attract each other, whereas like poles repel each other.