CBSE Solutions for Class 10 English

જવાબ : (a) Earthing
(b) Electric fuse

જવાબ : An electric motor works on the principle that when a current-carrying coil is placed in a magnetic field, it experiences a torque which tends to rotate it.

જવાબ : This is because of magnetic field of the bar magnet.

જવાબ : (a) Direction of magnetic field inside the loop is perpendicular to the plane of the paper inward (anticlockwise).
(b) Direction of magnetic field outside the loop is perpendicular to the plane of the paper outward (clockwise).

જવાબ : If the magnetic lines of forces intersect, there will be two different directions of magnetic field at that point, which is not possible.

જવાબ : When the length of current-carrying conductor and direction of magnetic field are perpendicular to each other, the maximum force is experienced by the current-carrying conductor.

જવાબ : Room heater and geyser.

જવાબ : Yes, when a current in coil A changes, magnetic field lines linked with coil B also change. Hence, due to change in number of magnetic field lines, there is an induced current in coil B. 

જવાબ : Direction of current – east to west as determined by Right-hand thumb rule. Ri’-lu-Uand Thumb Rule: If we hold a current-carrying conductor by right hand in such a way that the stretched thumb is along the direction of current, then the curly fingers around the conductor represents the direction of field lines of magnetic field.

જવાબ : For earth wire, green or yellow colour insulation is used. The earth wire provides the low resistance conducting path for the current and maintains the potential of appliances body with that of the earth. So, earth wire is used as a safety measure.

જવાબ : A compass needle is, in fact, a small bar magnet. If this is brought near another bar magnet, the like poles repel and the needle gets deflected.
40. Name the type of current:
(a) used in household supply. (b) given by a cell.
Answer.
(a) Alternating current. (b) Direct current.

જવાબ : In Fleming’s right hand rule,
thumb indicates — direction of motion of the conductor; forefinger indicates — direction of magnetic field.

જવાબ : This phenomenon is used in electric generator.

જવાબ : Perpendicular to the plane of paper in the outward direction by using Fleming’s left hand rule.

જવાબ : Yes, some current will be induced in the coil B. When the current in coil A is changed, some current is induced in the coil B. Due to change in current in coil A, the magnetic field lines linked with coil A and with coil B get changed. This sets up induced current in coil B.

જવાબ : Electric motor is used in the appliances like electric fans, washing machine, mixers, grinders, blenders, computers, MP3 players, etc.

જવાબ : When the conductor carries current in a direction perpendicular to the direction of the magnetic field, the force experienced by the conductor is largest.

જવાબ : (i) Current carrying conductor
(ii) Electromagnets
(iii) Permanent magnets

જવાબ : (i) Earthing and
(ii) Electric fuse.

જવાબ : Alternating current is produced by AC generators of nuclear power plants, thermal power plants, hydroelectric power stations, etc.

જવાબ : Some of the sources of direct current are dry cells, button cells, lead accumulators.

જવાબ : Different ways to induce current in a coil are :
1.    moving a magnet towards or away from the coil or vice-versa, and
2.    changing current in the neighbouring coil.

જવાબ : The split ring reverses the direction of current in the armature coil after every half rotation, i.e., it acts as a commutator. The reversed 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.

જવાબ : This is due to the fact that the resultant force on a north pole at any point can be only in one direction. But if the two magnetic field lines intersect one another, then the resultant force on north pole placed at the point of intersection will be along two directions, which is not possible.

જવાબ : Properties of magnetic lines of force :
•    The magnetic field lines originate from the north pole of a magnet and end at its south pole.
•    The magnetic field lines become closer to each other near the poles of a magnet but they are widely separated at other places.
•    Two magnetic field lines do not intersect one another.

જવાબ : 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.

જવાબ : The metallic body of electric appliances is earthed by means of earth wire. Any leakage of electric wire is transferred to the ground by means of earth wire. This prevents the user of the electric appliance from getting electric shocks. This is the reason why it is important for the metallic appliances to be earthed.

જવાબ : When the current in coil A changes, the magnetic field associated with it also changes. As a result the magnetic field around coil B undergoes change. The change in the magnetic field of coil B induces current in it.

જવાબ : A few devices in which electric motors are used are:
•    Electric fans
•    Water pumps
•    Mixers
•    Washing machines

જવાબ : When the direction of the current is perpendicular to the direction of the magnetic field is when the force experienced is the largest.

જવાબ : A few of the precautions to be taken to avoid the overloading of domestic electric circuits are as follows:
•    Connecting too many devices to a single socket should be avoided
•    Using too many appliances at the same time should be avoided
•    Faulty appliances should not be connected to the circuit

જવાબ : c. half revolution
When a rectangular coil is rotated in magnetic field, the direction of the induced current changes once in half revolution. As a result, the direction of the current in the coil remains the same.

જવાબ : Power plants and AC generators are some of the sources that produce alternating current.

જવાબ : DC generator and cell are some sources of direct current.

જવાબ : Electric generator works on the principle of electromagnetic induction. In a generator, electricity is generated by rotating a coil in the magnetic field.

જવાબ : Following are the different ways to induce current in a coil:
•    If the coil is moved rapidly between the two poles of horse shoe magnet, electric current is induced in the coil.
•    When a magnet is moved relative to the coil, an electric current is induced in the coil.

જવાબ : Split ring plays the role of commutator in an electric motor. The commutator reverses the direction of the current flowing through the coil after each half rotation of the coil. Due to this reversal of current, the coil continues to rotate in the same direction.

જવાબ : The working principle of electric motor is based on the magnetic effect of current. A current carrying conductor when placed in a magnetic field experiences force and rotates. The direction of the rotation of the conductor can be determined by Fleming’s Left hand rule.

જવાબ : Fleming’s Left hand rule states that if we arrange our thumb, forefinger and middle finger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the forefinger points towards the direction of magnetic field and the middle finger points towards the direction of current.

જવાબ : A current carrying conductor when placed in a magnetic field experiences force. The magnitude of this force will increase with the increase in the amount of current, length of conductor and the strength of the magnetic field. Hence, the strength of the magnetic force exerted on the rod AB and its displacement will increase if
1.    The current in rod AB is increased
2.    Stronger horse shoe magnet is used
3.    When the length of the rod AB increases

જવાબ : If two magnetic field lines intersect then at the point of intersection the compass needle shows two different directions, which is not possible, hence they do not intersect with each other.

જવાબ : Answer: north, south

જવાબ : solenoid

જવાબ : electrical, mechanical

જવાબ : mechanical, electrical

જવાબ : one, reverses

જવાબ : straight line

જવાબ : The compass needle is a small magnet. When the compass needle is brought close to a bar magnet, the magnetic field lines of the compass needle interact with the magnetic field lines of bar magnet, which causes the compass needle to deflect.

જવાબ : The properties of magnetic field lines are as follows:
•    Magnetic field lines do not intersect with each other.
•    They emerge from the North Pole and terminate at the South Pole.
•    Inside the magnet, the direction of the field lines is from the South Pole to the North Pole.

જવાબ : Fleming’s left hand rule
Statement : Stretch the left hand such that the thumb, first finger and the central finger are mutually perpendicular to each other. If the First finger points in the direction of the magnetic Field and the Central finger points in the direction of Current, then the thumb will point in the direction of Motion (or Force) as shown in figure 24.
 
Thus, in Fleming’s left hand rule, first finger shows the direction of the magnetic field. The central finger shows the direction of electric current flowing in the conductor. Thumb shows the direction of force on the conductor or the direction of motion of the conductor.

જવાબ :

1. Magnetic field lines are closed continuous curves.
2. The tangent at any point on the magnetic field line gives the direction of the magnetic field at that point.
3. No two magnetic field lines can cross each other.
4. Magnetic field lines are crowded in a region of strong magnetic field and magnetic field lines diverge in a region of weak magnetic field.

જવાબ : An electric motor is a device which converts electrical energy into mechanical energy.
Construction: It consists of a rectangular coil called armature curved magnet pieces, commutator and carbon brushes.
Principle: It works on the principle that when a current-carrying coil is placed normally in a magnetic field, it experiences a torque which tends to rotate it.
 
 

1. When a current flows through the coil, arms AB and CD experience a force. According to Fleming’s left hand rule, arm AB of the coil experiences a force in the downward direction. Similarly, arm CD of the coil experiences a force in the upward direction. Two equal and opposite forces constitute a couple and hence the coil will rotate in anticlockwise direction.
2. When the coil reaches the vertical position, no current flows in the coil and no force actstm the coil in this position.
3. Now coil rotates further and side AB is moved on the right, with its commutator segment touching the right hand brush so it has downward force acting it. Similarly, side CD has an upward force on it. Thus, the couple always acts in the same direction (clockwise) and the coil spins.

જવાબ : When a solenoid carrying current is freely suspended, it comes to rest along a particular direction because it behaves like a bar magnet with fixed polarities at its ends.

જવાબ : To avoid electric shocks, the metal body of an electrical device is ‘earthed’. A wire called ‘earth wire’ is used to connect the metal body of the electrical device to the earth, which is at zero potential. In household circuits, we have three wires, the live wire, the neutral wire and the earth wire. One end of the earth wire is connected to the device and the other end of the wire is connected to the earth. We now say that the device is “earthed” or “grounded”. Usually the three wires are connected to a three-pin plug. The neutral wire or the earth connection carries the high current to the earth from the device and prevents an electric shock.

જવાબ : Earth wire is a safety measure that provides a low resistance conducting path to the current. Sometimes due to excess heat or wear and tear, the live wire comes in direct contact with the metallic cover of the appliances, which can give an electric shock on touching them. To prevent from the shock the metallic part is connected to the earth through a three-pin plug due to which the current flows to the earth at the instant there is a short circuit.

જવાબ : (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) Fleming’s left hand rule : NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Stretch the forefinger, the central finger and the thumb of the left hand mutually perpendicular to each other. If the forefinger points in the direction of the magnetic field, the middle finger in the direction of current, then the thumb points in the direction of force in the conductor.
(iii) Fleming’s right hand rule : Stretch the thumb, forefinger and the central finger of the right hand mutually perpendicular to each other. If the forefinger points in the direction of magnetic field, thumb in the direction of motion of the conductor, then the middle finger points in the direction of current induced in the conductor.

જવાબ : Here the electron beam is moving from our back wall to the front wall, so the direction of current will be in the opposite direction, from front wall towards back wall or towards us. The direction of deflection (or force) is towards our right side.
We now know two things :

• direction of current is from front towards us, and
• direction of force is towards our right side.

જવાબ : A solenoid behaves like a magnet in the following ways.

• The magnetic field produced by a current carrying solenoid is very much similar to that of a bar magnet.
• Like a bar magnet, one end of the solenoid has N-polarity while the other end has S-polarity.

જવાબ : The electric generator works on the principle that when a straight conductor is moved in a magnetic field, then current is induced in the conductor.
In an electric generator, a rectangular coil is made to rotate rapidly in the magnetic field between the poles of a horse-shoe type magnet. When the coil rotates, it cuts the magnetic field lines due to which a current is produced in the coil.

જવાબ : As shown in figure alongside, each section of wire produces its concentric set of lines of force. By applying right hand thumb rule, we find that all the sections produce magnetic field downwards at all points inside the loop while at the outside points, the field is directed upwards. Therefore, the magnetic field acts normally into the plane of the paper at the points inside the loop and normally out of the plane of paper at points outside the loop.

જવાબ : A uniform magnetic field in a region is represented by drawing parallel straight lines, ail pointing in the same direction.
For example, the uniform magnetic field which exists inside a current-carrying solenoid can be represented by parallel straight lines pointing from its S-pole to N-pole (as shown in figure).

જવાબ : Fleming’s left hand rule : Stretch the first finger, the middle finger and the thumb of your left hand mutually perpendicular to each other in such a way that the first finger represents the direction of the magnetic field, the middle finger represents the direction of the current in the conductor, then the thumb will represent the direction of motion of the conductor.

જવાબ : Listed below are two instances of when a short-circuit can occur:

જવાબ : (i) When a bar magnet is pushed into the coil, current is induced in the coil momentarily as a result the galvanometer deflects in a particular direction momentarily.

જવાબ : An electric motor is a device that converts electrical energy to mechanical energy. It works on the principle of magnetic effect of current. The figure listed below shows a simple electric motor.

જવાબ : The direction of the magnetic field can be determined using the Fleming’s Left hand rule. The direction of the magnetic field will be perpendicular to the direction of current and the direction of deflection, i.e., either upward or downward. The direction of the current is from the front wall to the back wall because negatively charged electrons move from the back wall to the front wall. The directed of the magnetic force is rightward. Hence, using Fleming’s left hand rule it can be concluded that the direction of the magnetic field inside the chamber is downward.

જવાબ : Following are the methods of producing magnetic fields:

• By using a permanent magnet we can produce magnetic field and it can be visualized by spreading iron fillings on a white paper and keeping a magnet beneath the paper.
• A current carrying straight conductor produces magnetic field.
• Different types of conductors such as solenoid and circular loop can be used to see the presence of magnetic field.

જવાબ : The current drawn by the electric oven can be calculated using the formula

જવાબ : The safety measured commonly used in electric circuits are as follows:

1. Fuse

2. Earthing

જવાબ : The direction of the magnetic field can be determined using the Fleming’s Left hand rule. According to the rule, if we arrange our thumb, forefinger and the middle finger of the left hand right perpendicular to each other, then the thumb points towards the direction of the magnetic force, the middle finger the direction of current and the forefinger the direction of magnetic field. Since the direction of positively charged particle is towards west, the direction of the current will also be towards the west. The direction of the magnetic force is towards the north, hence the direction of magnetic field will be upward according to Fleming’s Left hand rule.

જવાબ :

જવાબ :

a. Electromagnetic induction
b. Concentric circles
c. Fuse

જવાબ :

a. Right hand thumb rule
b. Alternating current
c. Electric motor
d. Red