Solutions-NCERT-Class-10-Science-Chapter-12-Magnetic Effects of Electric Current-CBSE

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.

The magnetic field lines have the following properties:

• They originate from North pole of a magnet and end at its South pole, by convention.
• These lines are closed and continuous curves.
• They are crowded near the poles, where the magnetic field is strong and separated far from the poles, where the magnetic field is weak.
• Field lines never intersect with each other. If they do, that would mean that there are two directions of the magnetic field at the point of intersection, which is impossible.
• The relative strength of the magnetic field is shown by the degree of closeness of the field lines. Closer the lines, more will be the strength and farther the lines, less will be the magnetic field strength.

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 intersection, which is not possible.

Applying the right hand thumb rule, the magnetic field inside the loop is in vertically downward direction and outside the loop, it is in vertically upward direction.

In a uniform magnetic field, the magnetic field lines of force are parallel and equidistant from each other as shown in the diagram.

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

(d) momentum

Proton is a charged particle. When it moves in a magnetic field, a magnetic force is applied due to which its velocity and hence the momentum changes.

In Activity 12.7, 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 rod is increased, as force acting on rod is directly proportional to the current flowing through it. On increasing the current, force on the conductor increases.

(ii) If a stronger horse-shoe magnet is used, then the strength of magnetic field will increase leading to greater force on the rod. Due to this, the displacement of rod will increase.

(iii) Displacement of conductor is increased with an increase in length of the conductor. On increasing the length, more force will act on the conductor.

(d) upward

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 force is towards North. Thus, from Fleming's left hand rule, the direction of magnetic field is in upward direction.

(i) Earthing and, (ii) Electric fuse.

Given : P =  2 Kw = 2000 W, V = 220 V

The electric oven draws a current given by

I = P/V = 2000/220 = 9.09 A

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

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 not be used simultaneously.

(d) The field consists of concentric circles centred on the wire.

(c) increases heavily.

(i) True

(ii) False, the wire with green insulation is the earth wire not the live wire.

Two methods of producing magnetic field are as given below:

• Passing electric current through a straight conductor/circuit.
• Passing electric current through a circular loop.

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

According to Fleming's left hand rule, the direction of magnetic field inside the chamber is vertically downward.

(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 given the direction of the magnetic field.

(ii) Fleming's left hand rule: 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 central 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 directions of magnetic field, thumb in the direction of motion of the conductor, then the central finger points in the direction of current induced in the conductor.

As a result of live wire touching the neutral wire, the resistance offered to the flow of current becomes almost zero and this is called short-circuiting. In this situation, a large current flow through the circuit, causes a spark or damage to the appliance.

The earth wire connects the metallic body of the high powered appliance to the earth. It is a safety measure which ensures any leakage of current of 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.