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Effects of Electric Current - Magnetic Effect of Electric Current

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Topics

  • Introduction
  • Experiment 1
  • Experiment 2
  • Experiment 3

Introduction:

Hans Christian Oersted, a 19th-century scientist, discovered in 1820 that electric current creates a magnetic field. He observed that a magnetic needle near a current-carrying wire deflects, proving the connection between electricity and magnetism.

This discovery led to the development of electromagnetism, which is the basis of modern technology like electric motors and generators. In his honour, the unit of magnetic field intensity is named Oersted (Oe).

Hans Christian
Oersted (1777-1851)

A magnet is an object that attracts objects made of iron, cobalt, and nickel. A magnet comes to rest in a north-south direction when suspended freely. When current flows through a wire, it creates a magnetic field. This can be observed by the deflection of a compass needle placed near the wire. Winding the wire into a coil enhances this effect, creating an electromagnet, which is useful in various applications.

Properties of Magnet:

  1. A free suspended magnet always points towards the north and south directions.
  2. The pole of a magnet that points toward the north direction is called the north pole or north-seeking.
  3. The pole of a magnet that points toward the south direction is called the south pole or south-seeking.
  4. Like poles of magnets repel each other, while unlike poles of magnets attract each other.

Experiment 1

1. Aim: To demonstrate that a magnetic field is produced around a wire when an electric current flows through it.

2. Requirements: An inside tray of a used matchbox, a small magnetic needle, long connecting wire, an electric cell, a plug key, a light bulb, and a bar magnet.

3. Procedure

  • Place the magnetic needle inside the matchbox tray.
  • Wind the wire around the tray several times and connect it to an electric circuit with a cell, plug key, and bulb.
  • Mark the magnetic needle's initial position. Bring a bar magnet close to the needle and observe its movement.
  • Close the plug key to let current flow; the bulb lights up, and the magnetic needle changes position.
  • Open the plug key to stop the current; the needle returns to its original position.

Magnetic effect of current

3. Conclusion: When the current flows through the wire, the magnetic needle changes direction, indicating that a magnetic field is created around the wire. When the current stops, the magnetic needle returns to its original position. This experiment shows that electric current produces a magnetic field, a phenomenon first observed by Hans Christian Oersted.

Experiment 2

1. Aim: To observe the magnetic effect of electric current and its relation to the deflection of a magnetic needle.

2. Requirements: battery, plug key, thick copper wire, connecting wires, magnetic needle.

3. Procedure

  • Connect the circuit as shown in the diagram.
  • Place a magnetic needle near the copper wire between points A and B.
  • Keep the plug key open (circuit OFF) and observe the needle’s position.
  • Close the plug key (circuit ON) and note the deflection of the needle.
  • Reverse the connections of the cell and observe the new direction of the needle’s deflection.

Magnetic effects of a current

4. Observation

  • When the current flows through the wire, the magnetic needle deflects.
  • Reversing the current changes the needle’s deflection direction.

5. Conclusion: Electric current creates a magnetic field around a conductor. The field’s direction depends on the current flow. This principle is the basis of electromagnetism, used in motors and generators.

Experiment 3

1. Aim: To observe the magnetic field around a straight current-carrying conductor.

2. Requirements: battery, plug key, thick copper wire, cardboard, magnetic needle, iron filings.

3. Procedure

  • Set up the circuit as shown in the diagram.
  • Pass the thick copper wire vertically through the centre of the cardboard.
  • Close the key to allow a large current (about 1A or more) to flow through the wire.
  • Place a magnetic needle at different points around the wire and mark its directions.
  • Spread iron filings on the cardboard and gently tap it to observe the pattern formed.

Magnetic field produced around the conductor

4. Observation

  • The magnetic needle deflects in circular patterns around the wire.
  • Iron filings arrange in concentric circles, showing magnetic field lines.
  • The field strength decreases as the distance from the wire increases.
  • Increasing the current strengthens the magnetic field.

5. Conclusion: A current-carrying conductor generates a magnetic field around it. The magnetic field forms concentric circles around the wire.

The field strength decreases with distance from the wire. Increasing the current increases the strength of the magnetic field. This experiment confirms that electricity and magnetism are interrelated, forming the basis of electromagnetism.

If you would like to contribute notes or other learning material, please submit them using the button below.

Video Tutorials

We have provided more than 1 series of video tutorials for some topics to help you get a better understanding of the topic.

Series 1


Series 2


Shaalaa.com | Magnetic Effects of Current part 1 (Introduction)

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Magnetic Effects of Current part 1 (Introduction) [00:04:51]
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Magnetic Effects of Current part 1 (Introduction)
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Magnetic Effects of Current part 4 (Oersted Experiment)
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Related QuestionsVIEW ALL [69]

In the Activity shown below, how do we think the displacement of rod AB will be affected if

  1. current in rod AB is increased
  2. a stronger horse-shoe magnet is used
  3. length of the rod AB is increased?
  • Take a small aluminium rod AB (of about 5 cm). Using two connecting wires suspend it horizontally from a stand, as shown in Fig.
  • Place a strong horse-shoe magnet in such a way that the rod lies between the two poles with the magnetic field directed upwards. For this put the north pole of the magnet vertically below and south pole vertically above the aluminium rod (Fig.).
  • Connect the aluminium rod in series with a battery, a key and a rheostat.
  • Now pass a current through the aluminium rod from end B to end A.
  • What do you observe? It is observed that the rod is displaced towards the left. You will notice that the rod gets displaced.
  • Reverse the direction of current flowing through the rod and observe the direction of its displacement. It is now towards the right.
  • Why does the rod get displaced?


A current-carrying rod, AB, experiences a force perpendicular to its length and the magnetic field. Support for the magnet is not shown here, for simplicity.

A rectangular loop ABCD carrying a current I is situated near a straight conductor XY, such that the conductor is parallel to the side AB of the loop and is in the plane of the loop. If a steady current I is established in the conductor as shown, the conductor XY will ______.

A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminium rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions: 

  1. Why does the rod get displaced on passing current through it?
  2. State the rule that determines the direction of the force on the conductor AB.
    1. If the U-shaped magnet is held vertically and the aluminium rod is suspended horizontally with its end B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced?
    2. Name any two devices that use current carrying conductors and magnetic fields.

OR

Draw the pattern of magnetic field lines produced around a current carrying straight conductor held vertically on a horizontal cardboard. Indicate the direction of the field lines as well as the direction of current flowing through the conductor.

Paheli does not have a night lamp in her room. She covered the bulb of her room with a towel at the night to get dim light. Has she taken the right step? Give one reason to justify your answer.

The magnetic effect of current was discovered by:

(a) Maxwell
(b) Fleming
(c) Oersted
(d) Faraday

Name the scientist who discovered the magnetic effect of current.

What are MCBs? How do they work?

Which way does the wire in the diagram below  tend to move? 

 

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