Magnetic effects of electric current is an important chapter of class 10. It is just as important as Light, Reflection and Refraction. This topic lays the foundation for certain other important concepts in physics syllabus class 12th and have a diverse career in physics. Physicists like Albert Einstein and Issac Newton have made life-changing inventions in physics. Additionally, this topic has significant weightage with respect to entrance exams. All in all, Magnetic effects of electric current class 10 is a topic you must not skip. Through this blog, we provide you with important pointers that’ll help you with quick revision and the time of your exams.
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This Blog Includes:
- What is a Magnet?
- Magnetic fields
- Right-Hand Thumb Rule
- Magnetic Field Due to Current Through A Circular Loop
- Magnetic Field Due to Current In A Solenoid
- Force On A Current Carrying Conductor in A Magnetic Field
- Fleming’s Left-Hand Rule
- Electric Motor
- Electromagnetic Induction
- Electric Generator
- Domestic Electric Circuits
- Short circuit
- Practice Questions
What is a Magnet?
According to magnetic effects of electric current class 10, a magnet is an object that attracts or repels other magnetic materials (such as objects made of iron, cobalt and nickel) with its magnetic field. Properties of a magnet:
- When suspended freely, a magnet rests in a north – south direction.
- North pole of the magnet points towards the north.
- South pole of the magnet points towards the south.
- Like poles of a magnet repel while unlike poles of a magnet attract each other.
The area around a magnet where the influence of a magnet can be experienced is called magnetic fields. It has both magnitude and direction and the magnetic field and its field and direction are represented by magnetic lines of force. Three types of artificial magnets are bar magnets, magnetic needle and magnetic compass.
The magnetic field lines have various characteristics. They are mentioned below.
- The direction of the magnetic field emerges at the north pole and merges at the south pole. However inside the magnet, the field lines move from north pole to south pole.
- The magnetic field lines are closed curves.
- The degree of closeness of the field lines determine the relative strength of the magnetic field. (the more crowded the lines, stronger the field)
- The magnetic field lines do not cross each other.
Magnetic field lines due to a current carrying straight conductor
Also called the oersted’s experiment, found that the direction of flow of electric current determines the magnetic field through the current carrying conductor. If the current is flowing from south to north, then the direction of the magnetic field will be anticlockwise, and vice- versa. The direction of the magnetic field in relation to the current can also be determined through Right Hand Thumb Rule/ Maxwell’s Corkscrew Rule.
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Right-Hand Thumb Rule
According to magnetic effects of electric current class 10, Right Hand Thumb Rule is one way of finding out the direction of the current carrying conductor. Imagine a current carrying conductor is held in your right hand such that the thumb finger is pointing towards the direction of current. Then the fingers wrapped around the conductor will indicate the direction of the magnetic field lines.
Magnetic Field Due to Current Through A Circular Loop
Moving further in magnetic effects of electric current class 10, in a circular current carrying conductor, the magnetic field lines are represented by concentric circles at every point in the circular loop. The important features of the same are mentioned below.
- As we move away from the wire, the concentric circles appear larger and larger. At the centre of the circular coil, the arc appears as a straight line.
- The magnetic field is the strongest near the periphery of the loop.
- The magnetic field on the coil depends directly on the current passing through it. Therefore if the coil has n turns then the magnetic field is n times larger (the field due to each turn adds up) than a coil with a single turn.
- The direction of the current can be determined using the Right Hand Thumb Rule which is also called Maxwell’s corkscrew rule.
- As per this rule, if we imagine driving the corkscrew in the direction of the current, then the direction of the magnetic field is the same as the direction of the current.
Magnetic Field Due to Current In A Solenoid
According to magnetic effects of electric current class 10, a solenoid is a coil of many circular turns of insulated copper wire wrapped together in a cylindrical shape. When current is passed through the solenoid, it starts behaving like a bar magnet, where one end behaves like a north pole and the other end behaves like a south pole. The magnetic field lines inside the solenoid are in the form of straight lines therefore the field is uniform inside the solenoid. The solenoid is also used to magnetise a piece of magnetic material by placing it inside the coil. The object formed through this process is an electromagnet.
Force On A Current Carrying Conductor in A Magnetic Field
Next in magnetic effects of electric current class 10, we discuss the force on a current carrying conductor in a magnetic field. We know that the current passing through a conductor exerts a magnetic field. It was observed that the magnetic field exerts a force on a magnet, when it is placed in the area of the conductor. This phenomenon was first noticed by a French scientist Andre Marie Ampere. He also suggested that the magnet exerts an equal and opposite force on the conductor. When the direction of the current through the conductor is reversed, the direction of the force exerted on the object also changes. It was also found that the displacement is largest when the direction of the current is at right angles to the magnetic field. To ascertain the force of the conductor, a simple rule can be used.
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Fleming’s Left-Hand Rule
Magnetic effects of electric current class 10 talks about Fleming’s Left Hand Rule. According to Fleming’s Left Hand Rule, when you stretch your thumb, index finger and middle finger of your left hand such that they are perpendicular to each other, and the index finger points to the direction of the magnetic field and the middle finger points to the direction of the current, then the thumb finger will point in the direction of force in the conductor.
Many electronic devices (motor, generator, electronic devices, measuring instruments) work as per Fleming’s Left Hand Rule.
Electric motors are an important concept in Magnetic effects of electric current class 10. An electric motor is a device that converts electrical energy into mechanical energy. Electric motors are used in electric fans, various toys and for pumping water. Electric motors are of two types – A.C motors and D.C. motors.
Principal : when a rectangular coil is placed in a magnetic field and current is passed through it, the coil rotates continuously because of the force acting on it. The shaft attached to the coil also starts to rotate because of the rotation of the coil.
- When a current is supplied to the coil, a magnetic field is generated because of which the coil gets deflected.
- There is a split ring present in the coil, which on the coil reaching half way acts as a commutator and reverses the direction of current reversal in the direction of current leads to reversal in the direction of force acting on the coil.
- This change in the direction pushes the coil and it takes another half turn. This way the coil completes one turn around the axle.
- This process continued over several times keeps the motor in motion.
Next in Magnetic effects of electric current class 10, we will learn about electromagnetic Induction. Micheal Faraday, an English Physicist made a breakthrough recovery of how a moving magnet can generate electric current. The electricity produced as a result of this is known as electromagnetic induction.
Definition : When a conductor moves inside a magnetic field or alternatively, when the magnetic field changes around a conductor, then current is induced in a conductor. When a conductor is brought in motion because of a magnetic field, a potential difference is induced. This phenomenon is known as electromagnetic induction.
Fleming’s right hand rule
In Magnetic effects of electric current class 10, Fleming’s right hand rule helps explain electromagnetic induction.
Rule : When the index finger, middle finger and thumb are held in a way such that they are mutually perpendicular to each other and the index finger points to the direction of the magnetic, the middle finger points to the direction of induced current, then the thumb shows the movement of the conductor. When the magnetic field and motion of conductor are perpendicular to each other, then the induced current will be maximum.
From the exam point of view, Electrical generator is an important topic in Magnetic effects of electric current class 10. Let’s look at the structure and functioning of an electric generator:
- Electrical generator is a device that converts mechanical energy into electrical energy.
- Structurally an electric generator is like an electric motor. In an electric generator, an armature is placed in a magnetic field of a permanent magnet.
- Armature is attached to the wire and moveable around the axle. An electric field is induced when the armature moves within the electric field.
- On crossing the halfway mark of its rotation, the direction of the induced current changes. Because the direction of the current changes once in every rotation, the generator produces AC current.
- A split ring commutator helps convert AC generators into DC generators thus producing direct current.
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Domestic Electric Circuits
Let us now look at the Domestic Electric Circuits, its components and other related concepts in Magnetic effects of electric current class 10.
In our households, electricity is supplied through mains supported by poles or cables. There are three types of wires namely:
- Live wire (positive), usually with a red insulation cover.
- Neutral wire (negative) usually with a black insulation.
- Earth wire, to prevent leakage into a metallic body and ensures the user doesn’t get a serious shock.
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Short circuit occurs when the live wire and the neutral come in contact and a large current flows. This can happen due to either damage of insulation in power lines or faulty appliances.
At times, due to large flow of electric current in a circuit can lead to overheating of electric wire. Overheating of the wire may also cause a fire at times. In order to protect a device from overloading a fuse is inserted in a circuit. A fuse is a thin piece of wire that has a low melting point and a high resistance. A fuse is connected to the live wire and is always connected in series to the circuit.
Here are some practise questions that’ll help you test your understanding of the contents of this topic.
- Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(a) is zero.
(b) decreases as we move towards its end.
(c) increases as we move towards its end.
(d) is the same at all points.
- An electron enters a magnetic field at right angles to it. The direction of force acting on the electron will be
(a) to the right.
(b) to the left.
(c) out of the page.
(d) into the page
- A positively-charged particle (alpha-particle) projected towards the west is deflected towards north by a magnetic field. The direction of magnetic field is
(a) towards south
(b) towards east
- Which of the following properties of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)
- A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each
(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution
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