Free download NCERT Solutions for Class 10 Science Chapter 13 Magnetic effect of electric current in PDF form. NCERT Solutions for class 10 Science all chapters are also given in downloadable form.
NCERT Solutions for Class 10 Science Chapter 13
Class 10 Physics – Magnetic Effect of Electric Current
Important Questions for CBSE Exams – 2018
State the law of magnetic poles.
Law Of Magnetic Poles: It states that like poles repel while unlike poles of magnets attracts each other. Thus, two N-poles repels, two S-poles repel while N-pole attracts S-pole.
Give some basic properties of magnets.
Some basic properties of magnets are as follows:
(i) Attractive property: a magnet attracts small pieces of iron, cobalt, nickel, etc.
(ii) Directive property: a freely suspended magnet aligns itself nearly in the north-south direction.
(iii) Law of magnetic poles: Like magnetic poles repel and unlike magnetic poles attract each other.
(iv)Magnetic poles exist in pairs: If we break a magnet into two pieces, we always get two small dipoles magnets. It is not possible to obtain an isolated N-pole or S-pole.
Mention some important uses of magnets in everyday life.
Uses of magnets:
(i) Magnets are used in radio and stereo speakers.
(ii) They are used in video and audio cassette tapes, on the hard discs and floppies for computers.
(iii) They are used in almirah and refrigerator doors to snap them closed.
(iv) In children’s toys.
(v) In medicine, the magnetic resonance image (MRI) scanners expose the inner parts of the patient’s body for detailed examination by doctors.
What are magnetic lines of force? Give their important properties.
Magnetic lines of force:
A magnetic line of force may be defined as the curve the tangent to which at any point gives the direction of the magnetic field at that point. It may also be defined as the path along with a free north pole tends to move.
Properties of line of force:
(i) These are closed curves which start in air from N-pole and end at the S-pole and then return to the N-pole through the interior of the magnet.
(ii) No two magnetic lines of force can interest each other.
(iii) They start from and end on the surface of the magnet normally.
(iv)The lines of force have a tendency to contract lengthwise and expand sidewise. This explains attraction between unlike poles and repulsion between like poles.
(v) The relative closeness of the lines of force gives a measure of the strength of the magnetic field which is maximum at the poles.
Can two magnetic lines of force intersect? Justify your answer.
No, if two magnetic lines of force intersect, then there will be two tangents and hence two directions of magnetic field at the point of intersection. This is not possible.
What are magnetic field lines? How is the direction of a magnetic field at a point determined?
A magnetic field line may be defined as the path along with a unit north pole tends to move. The direction of magnetic field is determined by placing a small compass needle. The direction of deflection of N-pole of the compass needle gives the direction of the magnetic field at that point.
State Oersted observation. OR How can it be shown that a magnetic field exist around a wire through which a direct electric current is passing?
An magnetic needle brought close to a straight current carrying wire aligns itself perpendicular to the wire, reversing the direction of current reverses the direction of deflection. This shows that the current carrying wire is associated with a magnetic field.
Name and state the two rules for finding the direction of magnetic field produced by electric current through a straight conductor. OR State the law that helps to determine the direction of magnetic field around a straight current carrying conductor.
The direction of the magnetic field produced by a current carrying straight conductor can be obtained by using any of the following two rules:
(i) Right hand thumb rule: If the current carrying conductor is held in the right hand such that the thumb points in the direction of the current, then the direction of the curl of the fingers will give the direction of the magnetic field.
(ii) Maxwell’s corkscrew rule: If a right handed screw be rotated along the wire so that it advances in the direction of current, then the direction in which the screw rotates gives the direction of the magnetic field.
Why does a current-carrying conductor experience a force in a magnetic field?
We know that an electric current flowing through a conductor produces a magnetic field. This field exerts a force on a magnet placed near the conductor. In accordance with Newton’s Third law, the magnets must also exerts an equal and opposite force on the current carrying conductor. Thus a magnetic field exerts a force on a current-carrying conductor. Such a force was first suggested and demonstrated experimentally by French Scientist Andre Marie Ampere in 1820.
In what way can the magnitude of the induced current be increased ?
The magnitude of the induced current can be decreased by rapidly increasing or decreasing the number of magnetic field lines passing through a closed coil.
Explain the meaning of the term electromagnetic induction. In what factors does the value of induced current produced in a circuit depend? Name and state the rule used for determination of direction of induced current. State one practical application of this phenomenon in everyday life.
(i) The term electromagnetic induction means including electricity by magnetism. Whenever, the magnetic flux linked with a closed circuit changes, an induced potential and hence an induced current is set up in it. This phenomenon is called electromagnetic induction.
(ii) The value of current induced in a circuit depends on the rate of change of magnetic flux linked with the closed circuit.
(iii) Fleming’s right hand rule is used to find the direction of induced current.
(iv) Electric generator is an important practical application based on electromagnetic induction.
What are direct and alternating currents? OR What is difference between direct current and alternating current?
Direct Current: A direct current is that current which flows with constant magnitude in the same direction.
Alternating Current: An alternating current is that current whose magnitude changes continuously with time and whose direction reverses after equal intervals of time.
Distinguish between the terms ‘overloading’ and ‘short-circuiting’ as used in domestic circuits. OR Explain what is short-circuiting and overloading in an electric supply?
Short-circuiting: If due to defective or damaged wiring, the live and neutral wires come in direct contact, the resistance of the circuit becomes almost zero and an extremely large current flows through the circuit. This is called short circuiting. It results in heating the line wires and many damages the appliance. It may produce spark at the place of short circuit and cause fire. Short circuiting can be prevented by using an electric fuse in live wire.
Overloading: When a large number of high power appliances are switched on simultaneously, they draw extremely large current from the mains. If the current drawn from the mains exceeds the safety limit (5 A for domestic line and 15 A for power line), then this is known as overloading. As a result of overloading, the wires get over heated and the appliances may get damaged. This can be avoided by using an electric fuse in live wire.
What is the function of an earth wire? Why is it necessary to earth the metallic appliances?
Earthing: Earthing of an electrical appliance means connecting the metallic body of the high powered appliance (electric iron, toaster, refrigerator, oven, etc.,) to the earth through the earth wire in the domestic circuit. The earth wire has green insulation cover and is connected to a metal plate deep in the earth near the house and hence it is at zero potential.
Function and importance of earthing: If, by chance, the live wire touches the metallic body of the electrical appliance, its current flows to the earth through the earth wire, which provides a low resistance conducting path for the current. Thus, the earth wire (or earthing) is used as a safety measure which ensures any leakage of current to the metallic body of the appliance keeps its potential equal to that of the earth (zero volt) and the user may not get a severe electric shock.
In a household circuit, why are all the distribution circuit kept in parallel? OR What are the advantages of connecting different electrical appliances in parallel? Mention any three advantages.
It has the following advantages:
(i) If one line is overloaded, the fuse in this circuit only will be blown off, other distribution lines are protected.
(ii) There is a constant potential difference across each line.
(iii) If more lines are added in the circuit, it makes no difference to the other lines as p.d. is maintained at a constant value.