CBSE Class 10 Physics Magnetic Effect of Electric Current Worksheet Set C

 

Oersted Experiment :-
On passing the current through the copper wire XY in the circuit, the compass needle which is placed near the conductor gets deflected. If we reverse the direction of current, the compass needle deflect in reverse direction. If we stop the flow of current, the needle comes at rest.Hence, it concludes that electricity and magnetism are linked to each other. It shows that whenever the current will flow through the conductor, then the magnetic field around it will develop.
 

Magnetic Field – It is the region surrounding a magnet, in which force of magnet can be detected. It is a vector quantity, having both direction & magnitude.
Compass needle– It is a small bar magnet, whose north end is pointing towards the north pole and the south end is pointing towards the south pole of earth.
 

Magnetic field lines–
When a bar magnet is placed on a card board and iron filings are sprinkled, they will arrange themselves in a pattern as shown below.
The lines along which the iron filling align themselves represent magnetic field lines.
Hence, the magnetic field line is a path along which a hypothetical free north pole tends to move towards the south pole.

 

(1) The direction of magnetic field lines outside the magnet is always from north pole to south pole of bar magnet and are indicated by an arrow.Inside the magnet, the direction of field lines is from its south pole to north pole.Thus magnetic field lines are closed curve.
(2) The strength of the magnetic field is expressed by the degree of closeness of magnetic field lines. Closer the lines, more will be the strength and farther the lines, less will be the magnetic field strength.
(3) Two field lines will never intersect each other.If they intersect, then at the point of intersection the compass needle will show two directions of magnetic field which is not possible.

7. Magnetic field due to Current Carrying Conductor.

 

 

The above electric circuit in which a copper is placed parallel to a compass needle, shows the deflection in the needle gets reversed, when the direction of current is reversed. Hence electricity and magnetism are related to each other.

Right Hand Thumb Rule :–
It is a convenient way of finding the direction of magnetic field associated with the current carrying conductor.Hold the straight current carrying conductor in your right hand such that your thumb points towards the direction of current, then your folded fingers around the conductor will show the direction of magnetic field.

Magnetic Field due to Current through a Straight Conductor
The current carring conductor is intercepted by cardboard placed at right angle to the current caring conductor. There are some iron fillings sprinkled on the cardboard. When current flows through the conductor , the iron filings arrange themselves along the magnetic field.

Magnetic Field due to Current through a circular Loop
Every point on the wire carrying current gives rise to the magnetic field, appearing as a straight line at the centre of the loop. By applying the Right hand Thumb rule, we can find the direction of the magnetic field at every section of the wire.

Solenoid– A coil of many circular turns of insulated copper wire wrapped closely in the shape of a cylinder is called solenoid.
Magnetic field due to a current in a solenoid
Using R.H. Thumb Rule, we can draw the pattern of magnetic field lines around a current carrying solenoid.
– One end of the solenoid behaves as a magnetic north pole, while the other end behaves as the South Pole.
– The field lines inside the solenoid are in form of parallel straight lines, that implies that magnetic field inside the solenoid is same at all points i.e. field is uniform inside the solenoid .

Magnetism of the solenoid can be increased
By increasing the number of turns of the coil
By increasing the strength of current
By using a metal core like soft iron

Force on a current carrying conductor in a magnetic field.
Andre Marie Ampere suggested that the magnet also exert an equal and opposite force on the current carrying conductor.
We will observe that the rod will displace i.e. the rod will experience a force, when it is placed in a magnetic field, in a perpendicular direction to its length.
– The direction of the exert force will be reversed if the direction of current through the conductor is reversed.
– If we change the direction of the field by interchanging the two poles of the magnet, again the direction of exert force will change.
– Therefore the direction of exerted force depends on
(1) direction of current
(2) direction of magnetic field lines.

Fleming's Left Hand Rule

According to this rule, stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular to each other.
If the fore finger represents the direction of the magnetic field & middle finger represents the direction of current, then the thumb will point in the direction of motion or force acting on the conductor.
Functioning of electric motors is based on this rule. It converts electrical energy into mechanical energy.

Galvanometer-
It is an instrument that can detect the presence of a current in a circuit. If the pointer is at zero (the centre of scale) then there will be no flow of current.If the pointer deflects on either side right or left, this will show the direction of current. Represented by

Direct Current and alternative current
1) Direct current (DC):- Does not change its direction with time it is unidirectional.
2) Alternate Current (AC) :- Changes the direction periodically after equal interval of time.

Advantages of Alternate Current (AC) over Direct Current (DC)
Electric power can be transmitted to longer distances without much loss of energy. Therefore cost of transmission is low.
In India the frequency of AC is 50Hz. It means after every 1/100 second it changes its direction.

Domestic Electric Circuits :–
In our homes, the electric power supplied is of potential difference V = 220V

It consist of three wires :–
(1) Wire with red insulation cover – LIVE WIRE (POSITIVE)
Live wire is at high potential of 220V
(2) Wire with black insulation cover – NEUTRAL WIRE (NEGATIVE)
Neutral wire is at zero potential
Therefore, the potential difference between the two is 220V.
(3) Wire with Green insulation cover – EARTH WIRE
It is connected to a copper plate deep in the earth near the house.

Earthing-A safety measure: The metallic body of the appliances is connected with the earth wire as a safety measure.
Earth wire provides a low resistance to the current hence any leakage of current to the metallic body of the appliances, keep its potential equal to that of earth. That means zero potential and the user is saved from severe electric shocks.

Fuse:-
Electric fuse is an important component of all domestic Circuits. A fuse in a circuit prevents damage to the appliances and the circuit due to overloading.
Overloading can occur when the live wire and the neutral wire come into direct contact. In such a situation, the current in the circuit abruptly increases. This is called short- circuit.
The use of an electric fuse prevents the electric circuits and appliances from possible damage by stopping the flow of unduly high electric current.
Overloading can also occur due to an accidental hike in the supply voltage.
Overloading may be caused by connecting too many appliances to a single socket

 

MCQ Questions for NCERT Class 10 Science Magnetic Effects of Electric Current

Question. Which among of these are the main characteristics of fuse element?
(a) High conductivity
(b) low melting point
(c) do not bum due to oxidation
(d) All of the above

Very Short Answer :

 

Answer: Miniature circuit breakers are used in the domestic wiring.

 

Answer: The alternating current produced in India has a frequency of 50 Hz.

 

Answer: The red color wire is the live wire and the black color wire is for the neutral wire.

Question. State important features of the magnetic field obtained inside the solenoid. Write one use of solenoid.
Answer: The field lines inside the solenoid are parallel and closely spaced showing the field is highly uniform, same in strength at all the points and in the same direction.
Solenoid is used for making electromagnet.

Question. Give one difference between the wires used in the element of an electric heater and in a fuse.
Answer: Electric wire used in electric heater has a high melting point whereas fuse wire has a low melting point.

Question. What is the direction of magnetic field lines inside and outside of a bar magnet?
Answer: Direction of magnetic field lines:
Inside a bar magnet: from South pole to North pole.
Outside of a bar magnet: from North pole to a South pole.

Question. What will the polarity be of one end of a solenoid if the current appears to be flowing anticlockwise in it ?
Answer: North pole by using Clock Face Rule.

Question. A magnet is hung using a string. How will you identify the poles?
Answer: The north seeking pole is north pole and the south seeking pole is south pole.