SCIENCE || CLASS 10TH || CHAPTER 13 || INTEXT QUESTIONS AND ANSWERS || CBSE AND MP BOARD

  "AKC SCIENCE CLASSES"

CLASS 10 TH (CBSE AND MP BOARD)

CHAPTER 13

MAGNETIC EFFECTS OF ELECTRIC CURRENT

INTEXT QUESTIONS AND ANSWERS

NCERT INTEXT QUESTIONS (PAGE NO. 224)

Q.01:- Why does a compass needle get deflected when brought near a bar magnet?

Ans:- The magnetic field of the magnet exerts force on both the poles of the compass needle. The forces experienced by the two poles are equal and opposite. These two forces form a couple which deflects the compass needle.

NCERT INTEXT QUESTIONS (PAGE NO. 228)

Q.01:- Draw magnetic field lines around a bar magnet.

Ans:- 

Q.02:- List the properties of the magnetic line of force.

Ans:- Properties of magnetic line of force are :-

• They travel from north pole to south pole outside the magnet and south pole to north pole inside the magnet.
• They are closed and continuous curves.
• Two magnetic field lines never intersect each other. If the lines intersect, then at the point of intersection there would be two directions (the needle would point towards two directions) for the same magnetic field, which is not possible.
• The number of field lines per unit area is the measure of the strength of magnetic field, which is maximum at poles. The magnetic field is strong, where the field lines are close together and weak where the lines are far apart.

Q.03:- Why do two magnetic field lines of force never intersect each other?

Ans:- Two magnetic field lines of force never intersect each other. If the lines intersect, then at the point of intersection there would be two directions (the needle would point towards two directions) for the same magnetic field, which is not possible.

NCERT INTEXT QUESTIONS (PAGE NO. 229-230)

Q.01:- Consider loop of wire lying in the plane of 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.

Ans:- Since the current passes through the loop in clockwise direction, therefore, the front face of the loop will be the south pole and the black face, i.e., the face touching the table will be north pole. According to right-hand rule, the direction of magnetic field inside the loop will be pointing downward. Outside the loop, the direction of the magnetic field be upward.

Q.02:- The magnetic field in a given region is uniform. Draw a diagram to represent it.

Ans:- A uniform magnetic field in a region is represented by drawing parallel and equidistant straight lines, all pointing in the same direction.

Q.03:- Choose the correct option. The magnetic field inside a long straight solenoid carrying current 

(ⅰ) is zero.

(ⅱ) decreases as we move towards its ends.

(ⅲ) increases as we move towards its ends.

(ⅳ) is the same at all points.

Ans:- The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. Thus, answer (ⅳ) is correct.

NCERT INTEXT QUESTIONS (PAGE NO. 231-232)

Q.01:- 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.

Ans:- The correct option are (c) and (d). The magnetic force acts perpendicular to the direction of motion of the proton. It does not change its mass and speed but changes its direction of motion. So both velocity and momentum get changed.

Q.02:- In Activity 13.7 (NCERT Textbook), 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) lengths of the rod AB is increased.

Ans:- (ⅰ) When a stronger horse-shoe magnet is used, the magnitude of the magnetic field increases. This is increases the force exerted on the rod and the displacement of the rod.

(ⅱ) When a stronger horse shoe magnet is used, the magnet is used, the magnitude of the magnetic field increases. This increases the force exerted on the rod and the displacement of the rod.

(ⅲ) The displacement of the rod will increase, because F ∝ L.

Q.03:- A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is

(a) Towards south

(b) towards east

(c) downward

(d) upwards

Ans:- The correct option is (d). This is in accordance with Fleming's left hand rule.

NCERT INTEXT QUESTIONS (PAGE NO. 233)

Q.01:- State Fleming's left-hand rule.

Ans:- According to Fleming's left hand rule, if we stretch the forefinger, the central finger and thumb of our left hand mutually perpendicular to each other and if the forefinger points in the direction of the magnetic field, the central finger in the direction of current, then the thumb will point in the direction of motion or the force on the conductor.

Q.02:- What is the principle of an electric motor?

Ans:- A current carrying conductor when placed in a magnetic field experiences a force. The direction of this force is given by Fleming's left hand rule. This is the basis of an electric motor.

Q.03:- What is the role of the split ring in an electric motor?

Ans:- The split ring reverses the direction of current in the armature coil after every half rotation, i.e., it acts as a commutator. The reversal of current reverses the direction of the forces acting on the two arms of the armature after every half rotation. This allows the armature coil to rotate continuously in the same direction.

NCERT INTEXT QUESTIONS (PAGE NO. 236)

Q.01:- Explain different ways to induce current in a coil.

Or

List two different ways of including current in a coil.

Ans:- A current can be induced in a coil by

• moving a magnet towards or away from the coil or vice versa, and
• changing current in the neighbouring coil.

NCERT INTEXT QUESTIONS (PAGE NO. 237)

Q.01:- State the principle of an electric generator.

Ans:- An electric generator works on the principle of electromagnetic induction. When a closed coil is rotated in a uniform magnetic field with its axis perpendicular to the direction of the field, the magnetic field lines passing through the coil change and an induced potential difference and hence a current is set-up in it.

Q.02:- Name some sources of direct current.

Ans:- Some of the sources of direct current ary dry cells, button cells, lead accumulators, etc.

Q.03:- Which sources produce alternating current?

Ans:- Alternating current is produced by a.c. generators of nuclear power plants, thermal power plants, hydroelectric power stations, etc.

Q.04:- 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 revolutions

(c) half revolutions

(d) one-fourth revolution.

Ans:- The correct option is (b).

NCERT INTEXT QUESTIONS (PAGE NO. 238)

Q.01:- Name two safety measures commonly used in electric circuits and appliances.

Ans:- The safety measures commonly used in electric circuits and appliances are :-

• Earthing and,
• Electric fuse.

Q.02:- An electric oven of 2 KW power rating is operated in a domestic electric circuit (220V) that has a current rating of 5 A. What result do you expect? Explain.

Ans:- The electric oven draws a current given by

I = P/V = 2KW/220V = 2000W/220V = 9.09 A.

Thus the electric oven draws current much more than the current rating of 5A. That is the circuit is overloaded. Due to excessive current, the fuse wire blows and the circuit is broken.

Q.03:- What precaution should be taken to avoid the overloading of domestic electric circuits?

Ans:- As a result of overloading, the connecting wires get over-heated and the appliances may get damaged. To avoid this, the following safety measures must be taken :-

• The wires used in the circuit must be coated with good insulating materials like PVC, etc.
• The circuit must be divided into different sections and a safety fuse must be used in each section.
• High power appliances like air-conditioner, refrigerator, water heater, etc., should be used simultaneously.