# Magnetic Effects Of Electric Current – Chapter 13 (NCERT Solutions & All Extra And Important Questions) – Science (Class 10)

SUBJECT SCIENCE
CLASS X (10th)
QUESTION FROM – Magnetic Effects Of Electric Current – Chapter 13
ALL EXTRA & IMPORTANT / EXERCISE QUESTION ANSWER

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#### Intext Questions – Magnetic Effects Of Electric Current – Chapter 13 (NCERT Solutions & All Extra And Important Questions) – Science (Class 10)

Q1. Why does a compass needle get deflected when brought near a bar magnet?
Answer – The compass needle gets deflected due to the magnetic field around a bar magnet.

Q2. Draw magnetic field lines around a bar magnet.
Answer – Q3. List the properties of magnetic field lines.

Q4. Why don’t two magnetic field lines intersect each other?
Answer – If two magnetic lines of force intersect each other it would mean that there are two directions of the magnetic field at the point of intersections, which is not possible.

Q5. Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.
Answer – Applying the right-hand thumb rule, the magnetic field inside the loop is in vertically downward and outside the loop, it is in vertically upward directions.

Q6. The magnetic field in a given region is uniform. Draw a diagram to represent it.
Answer – In a uniform magnetic field, the magnetic field lines of force are parallel and equidistant from each other as shown in the diagram.

Q7. 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.
Answer – (d) Magnetic field inside a solenoid is the same at all the points.

Q8. Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)
(a) mass (b) speed (c) velocity (d) momentum,
Answer – (d) Proton is a charged particle. When it moves in a magnetic field, a magnetic force is applied due to its velocity and hence the momentum changes.

Q9. In Activity 13.7, how do we think the displacement of rod AB will be affected if
(i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used, and (iii) length of the rod AB is increased?

Answer – In Activity 7, the force acting on a current carrying conductor when placed in a magnetic field is illustrated.
(i) When current in rod AB is increased, the displacement of the rod is increased, as a force acting
on the rod is directly proportional to the current flowing through it. On increasing the current, force on the conductor increases.
(i) If a stronger horse-shoe magnet is used, then the strength of the magnetic field will increase leading to greater force on the rod. Due to this, the displacement of rod will increase.
(ii) Displacement of the conductor is increased with an increase in length of the conductor. On increasing the length, more force will act on the conductor.

Q10. 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 (c) downward (d) upward.
Answer – The positively charged particle is moving towards West, i.e. the direction of current is towards West (current flows in the direction of the motion of positive charge). The particle is deflected towards North, so the direction of the force is towards North. Thus, from Fleming’s left-hand rule, the direction of the magnetic field is in an upward direction.

Q11. State Fleming’s left-hand rule.

Q12. What is the principle of an electric motor

Q13. What is the role of the split ring in an electric motor?
Answer – Split rings act as a commutator and its a function is to reverse the direction of current flowing through the coil.

Q14. Explain different ways to induce current in a coil.
Answer – Current is induced in a coil in the following ways:
(i) When a magnet is moved towards or away from the coil or there is a relative motion between coil and magnet, a current is induced in the coil circuit.
(ii) When a current passing through a coil a coil changes, then a current is induced in a coil placed near it.

Q15. State the principle of an electric generator.

Q16. Name some sources of direct current.
Answer – Some sources of direct current are electrochemical dry cells, solar cells, lead-acid accumulator batteries, DC generators, etc.

Q17. Which sources produce an alternating current?
Answer – Some sources that produce alternating current are AC generators, thermal power stations, car alternators, etc.

Q18.  Choose the correct option. 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
Answer – After half revolution, the direction of motion of rectangular cool changes. Thus, the direction of induced current changes.

Q19. Name two safety measures commonly used in electric circuits and appliances.
Answer –  Electric fuse and earth wire are two safety measures commonly used in electric circuits.

Q20. An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
Answer – Since, current drawn by the oven is greater than the rated value of current, which may cause overloading and excessive heating of the circuit.

21. What precaution should be taken to avoid the overloading of domestic electric circuits?
Answer –  The following precautions should be taken to avoid the overloading domestic electric circuits as given below:
(i) The circuits should be of proper current rating and appliances should be connected accordingly.
(ii) Wires should be checked from time to time those wires whose insulation is worn, should be immediately replaced.

(iii) Connection of too many appliances in a single socket must be avoided.

#### Exercise Questions – Magnetic Effects Of Electric Current – Chapter 13 (NCERT Solutions & All Extra And Important Questions) – Science (Class 10)

Q1.  Which of the following correctly describes the magnetic field near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
Answer – (d) The magnetic field lines due to a straight current carrying wire are concentric circles with the centre on the wire.

Q2.  The phenomenon of electromagnetic induction is
(a) the process of charging a body.
(b) the process of generating magnetic field due to a current passing through a coil.
(c) producing induced current in a coil due to relative motion between a magnet and the coil.
(d) the process of rotating a coil of an electric motor.
Answer – (C) The process of producing induce current in a coil due to relative motion between a magnet and the coil is known as electromagnetic induction.

Q3. The device used for producing electric current is called a
(a) generator. (b) galvanometer. (c) ammeter. (d) motor.
Answer – (a) Generator converts mechanical energy to electrical energy.

Q4. The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has parmanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
Answer – AC generator has slip rings while DC generator has split rings as commutator. Due to slip Rings the current produced by AC generator flows in both the direction while current produced by DC generator flows in single direction.

Q5. At the time of short circuit, the current in the circuit
(a) reduces substantially. (b) does not change. (c) increases heavily. (d) vary continuously.

Q6.  State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire of an electric supply.
Answer – (a) False, electric motor converts electrical energy into mechanical energy.
(b) True,
(c) True,
(d) False, The wire with green insulation is the earth wire and not the live wire.

Q7. List two methods of producing magnetic fields.
Answer –  Three methods of producing magnetic field are as given below
(i). Passing Electric current through a straight conductor.
(ii). Passing Electric current through a circular loop.
(iii). Passing Electric current through a solenoid.

Q8. How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.
Answer –  A solenoid behaves like a magnet when the electric current passes through it.
One end of a solenoid behaves as a North Pole and the other end behaves as a South Pole. Use a bar magnet to determine the North and South poles of a current carrying solenoid by using the property, like poles repel and unlike poles attract each other. The end of the solenoid which attracts north pole of a bar magnet is magnetic South Pole of the solenoid. The end of the solenoid which repels the north pole of a bar magnet is the magnetic north pole of the solenoid.

Q9. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?
Answer – The force experienced by a current carrying conductor placed in a magnetic field is the largest when the conductor is kept perpendicular to the direction of the magnetic field.

Q10. Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of the magnetic field?
Answer – According to Fleming’s left-hand rule, the direction of magnetic field is vertically downward.

Q11. Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?

Q12. Name some devices in which electric motors are used.
Answer – Some Devices in which electric motors are used are electric fans, refrigerator, mixers, washing machines, computers etc.

Q13.  A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is
(i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary inside the coil?
Answer – The Galvanometer shows a deflection which means current is induced in the coil. Current is induced in the coil due to the relative motion between coil and magnet.
The Galvanometer shows a deflection in opposite direction which means current is induced in the opposite direction in this case the direction of motion is in the opposite direction w.r.t coil. There is no deflection in the Galvanometer has no current is induced in the coil this is because there is no relative motion between coil and magnet.

Q14.  Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
Answer – Yes current will be induced in the coil B. When the current in the coil A is changed, The magnetic field around it changes. As the coils are close to each other the magnetic field around coil B changes and hence induces a current in coil B.

Q15. State the rule to determine the direction of a
(i) Magnetic field produced around a straight conductor-carrying current,
(ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and  (iii) current induced in a coil due to its rotation in a magnetic field.

Q16. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?

Q17. When does an electric short circuit occur?
Answer – An electric short circuit occurs when the insulation of wires is damaged or there is a fault in the appliance. Due to this the live and neutral wire come in direct contact and the current in the circuit increases abruptly.

Q18. What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Answer – The earth wire is connected to a metallic plate buried deep inside the earth. In this way, the metallic body of the appliance is connected to the Earth, which provides a low resistance conducting path for electric current. Hence, Any leakage of current to the metallic body of the appliance to the earth through each wire. The use and might not get a severe electric shock on touching search and appliances in case of a fault

#### Examples Questions – Magnetic Effects Of Electric Current – Chapter 13 (NCERT Solutions & All Extra And Important Questions) – Science (Class 10)

Example 13.1A current through a horizontal power line flows in east to west direction. What is the direction of magnetic field at a point directly below it and at a point directly above it?
Solution The current is in the east-west direction. Applying the right-hand thumb rule, we get that the magnetic field (at any point below or above the wire) turns clockwise in a plane perpendicular to the wire, when viewed from the east end, and anti-clockwise, when viewed from the west end.

Example 13.2 – An electron enters a magnetic field at right angles to it, as shown in Fig. 13.14. 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.
Solution Answer is option (d). The direction of force is perpendicular to the direction of magnetic field and current as given by Fleming’s left hand rule. Recall that the direction of current is taken opposite to the direction of motion of electrons. The force is therefore directed into the page.