IMPORTANT DIAGRAMS��PHYSICS
Class :- X
Subject :- Science
Name of Teacher :- Mr. V. K. Pathak (PGT Phy)
School :- KV RRL Jorhat, Assam
Symbols of components used in electric circuits:-
A
v
+
-
-
+
+
-
+
-
An electric cell A battery or combination
of cells
Plug key or switch Plug key or switch
(open) (closed)
Electric bulb A resistor of
resistance R
Variable resistance or
or rheostat
Ammeter Voltmeter
A wire joint A wire crossing over
without joining
Ohm’s law :-
Ohms law is a relationship between the potential difference across a conductor and the current flowing through it.
Ohm’s law states that :-
‘The current flowing through a conductor is directly proportional to the potential difference between its ends provided its temperature remains constant.’ I α V or V α I Therefore V= IR
Where R is a constant called resistance for a given metallic wire at a given temperature.
Verification of Ohm’s law :-
V
A
+
-
+
-
+
-
R
K
A
B
( )
Resistors in series :-
( )
A
R1
R2
R3
+
+
-
-
V1
V2
V3
A
B
V
+
-
When three resistors R1, R2 and R3 are connected in series across AB
i) The current in all the resistors is the same.
ii) The total voltage (PD) across the resistors is equal to the sum of the
voltage across each resistor.
V = V1 + V2 + V3
iii) The eqvivalent resistance is the sum of the resistances of each
resistor.
RS = R1 + R2 + R3
Resistors in parallel :-
R1
R3
R2
( )
A
I1
I2
I3
+
-
+
-
A
B
V
+
-
When three resistors R1, R2 and R3 are connected in parallel across AB,
i) The voltage (PD) in all the resistors is the same.
ii) The total current in all the resistors is the sum of the current in each
resistor. I = I1 + I2 + I3
iii) The reciprocal of the equivalent resistance is the sum of the
reciprocals of each resistance.
I/Rp= 1/R1 +1/R2 +1/R3
Heating effect of electric current :-
If a current I flows through a resistor of resistance R and t be the time for which a charge Q flows through it, then the work done to move the charge through potential difference V
W = Q X V
P = W = Q X V Q = I or P = V X I
t t t
or Heat energy supplied = P X t = V X I X t
According to Ohm’s law V = IR
Heat produced H = I2Rt
( )
A
V
R
A
B
I
I
+
-
+
-
+
-
THE HUMAN EYE
��
�
0
Defects of vision and their correction :-
i) Myopia or near sightedness :-
Myopia is a defect of vision in which a person can see nearby
objects clearly but cannot see distant objects clearly because the
image is formed in front of the retina.
This may be due to:-
i) Increase in curvature of the eye lens
ii) Increase in the length of the eye ball
It can be corrected by using suitable concave lens.
Myopic eye
Correction using concave lens
ii) Hypermetropia or far sightedness :-
Hypermetropia is a defect of vision in which a person can see
distant objects clearly but cannot see nearby objects clearly because
the image is formed behind the retina.
This may be due to:-
i) Decrease in curvature of eye lens
ii) Decrease in the length of the eye ball
It can be corrected by using a suitable convex lens.
Hypermetropic eye
Correction using convex lens
Refraction of light through a glass prism :-
When a ray of light passes through a glass prism, it gets bent twice at the air- glass interface and glass- air interface.
The emergent ray is deviated by an angle to the incident ray.This angle is called the angle of deviation.
Incident ray
Refracted ray
Emergent ray
D
i
r
Air
Glass
Glass
Air
Glass prism
e
Angle of emergence
Angle of deviation
Normal
Dispersion of white light by a glass prism :-
When a beam of white light is passed through a glass prism, it is split up into a band of colours called spectrum. This is called dispersion of white light. The spectrum of white has the colours violet, indigo, blue, green, yellow, orange and red (VIBGYOR). The red light bends the least and the violet light bends the most.
Beam of white light
Spectrum
R
O
Y
G
I
B
V
Glass prism
Recombination of the spectrum of white light � produces white light :-
R
V
V
R
R
When a beam of white light is passed through a glass prism, it is split up into its component colours. When these colours are allowed to fall on an inverted glass prism it recombines to produce white light.
V
White light
White light
Glass prisms
Rainbow formation :-
A rainbow is a natural spectrum appearing in the sky after a rain shower. It is caused by the dispersion of sunlight by water droplets present in the atmosphere. The water droplets act like small prisms. They refract and disperse the sunlight then reflect it internally and finally refract it again when it comes out of the rain drops. Due to the dispersion of sunlight and internal reflection by the water droplets we see the rainbow colours.
Sunlight
Raindrop
Red
Violet
Refraction and dispersion
Internal reflection
Observer
Refraction
Atmospheric refraction :-
Atmospheric refraction is due to the gradual change in the refractive index of the atmosphere. The refractive index of the atmosphere gradually increases towards the surface of the earth because the hot air above is less dense than the cool air below. So light gradually bends towards the normal. So the real position of a star is different from its apparent position.
Apparent position
Real position
Eye
Star
Increasing
refractive index
of atmosphere
Earth
Observer
Sunrise
Sunset
Apparent position
Apparent position
Atmosphere
Advance sunrise and delayed sunset :-
The sun is visible to us about 2 minutes before sunrise and about two minutes after sunset due to atmospheric refraction.
The apparent flattening of the sun’s disc at sunrise and at sunset is also due to atmospheric refraction.
Horizon
Horizon
Real position
Real position
Reflection by spherical mirrors :-
i) In a concave mirror a ray of light parallel to the principal axis after reflection passes through the focus.
In a convex mirror a ray of light parallel to the principal axis after reflection appears to diverge from the focus.
C F P P F C
ii) In a concave mirror a ray of light passing through the � focus after reflection goes parallel to the principal axis.
In a convex mirror a ray of light directed towards the focus after reflection goes parallel to the principal axis.
C F P P F C
iii) In a concave mirror a ray of light passing through the � centre of curvature after reflection is reflected back along � the same direction.
In a convex mirror a ray of light directed towards the centre of curvature after reflection is reflected back along the same direction.
C F P P F C
iv) In a concave or a convex mirror a ray of light directed obliquely at the pole is reflected obliquely making equal angles with the principal axis.
C F i P i P F C
r r
Images formed by concave mirror :-
i) When the object is at infinity the image is formed at the focus, it is highly diminished, real and inverted.
C F P
ii) When the object is beyond C, the image is formed between C and F, it is diminished, real and inverted.
C F P
v) When the object is at F, the image is formed at infinity, it is highly enlarged, real and inverted.
C F P
vi) When the object is between F and P, the image is formed behind the mirror, it is enlarged, virtual and erect.
C F P
Images formed by convex mirror :-
i) When the object is at infinity, the image is formed at F behind the mirror, it is highly diminished, virtual and erect.
P F
ii) When the object is between infinity and pole, the image is formed behind the mirror, it is diminished, virtual and erect.
P F C
Refraction of light through a rectangular glass � slab :-
When a ray of light passes through a rectangular glass slab, it gets bent twice at the air- glass interface and at the glass- air interface.
The emergent ray is parallel to the incident ray and is displaced through a distance.
i
e
Normal
Incident ray
Emergent ray
Refracted ray
Glass
Air
Normal
r
Glass
Air
Rectangular glass slab
displacement
Angle of emergence
Angle of incidence
Angle of refraction
Refraction by spherical lenses :-
i) In a convex lens a ray of light parallel to the principal axis after refraction passes through the focus on the other side of the lens. In a concave lens it appears to diverge from the focus on the same side of the lens.
2F1 F1 O F2 2F2 2F1 F1 O F2 2F2
ii) In a convex lens a ray of light passing through the focus after refraction goes parallel to the principal axis. In a concave lens a ray of light directed towards the focus after refraction goes parallel to the principal axis.
2F1 F1 O F2 2F2 2F1 F1 O F2 2F2
iii) In a convex lens and concave lens a ray of light passing through the optical centre goes without any deviation.
2F1 F1 O F2 2F2 2F1 F1 O F2 2F2
Images formed by convex lens :-
i) When the object is at infinity the image is formed at the focus F2, it is highly diminished, real and inverted.
2F1 F1 O F2 2F2
ii) When the object is beyond 2F1, the image is formed between F2 and 2F2, it if diminished, real and inverted.
2F1 F1 O F2 2F2
iii) When the object is at 2F1, the image is formed at 2F2, it is the same size as the object, real and inverted.
2F1 F1 O F2 2F2
iv) When the object is between 2F1 and F1, the image is formed beyond 2F2, it is enlarged, real and inverted.
2F1 F1 O F2 2F2
v) When the object is at F1 the image is formed at infinity, it is highly enlarged, real and inverted.
2F1 F1 O F2 2F2
vi) When the object is between F1 and O, the image is formed on the same side of the lens, it is enlarged, virtual and erect.
2F1 F1 O F2 2F2
Images formed by concave lens :-
i) When the object is at infinity, the image is formed at the focus F1 on the same side of the lens, it is highly diminished, virtual and erect.
F1 O
ii) When the object is between infinity and F1, the image is formed between F1 and O on the same side of the lens, it is diminished, virtual and erect.
FI O
Magnetic field lines :-
Magnetic field lines are the paths around a magnet along which the north pole of a magnetic compass needle tends to move.
The magnetic field lines around a magnet can be observed by sprinkling iron filings around a magnet. It can also be observed by moving a magnetic compass around a magnet.
i) The magnetic field lines emerge at the north pole and merge at the
south pole.
ii) The magnetic field lines are closer at the poles.
iii) The magnetic field lines do not intersect each other.
Magnetic field due to a current carrying conductor :-
If a magnetic compass is placed near a conductor carrying current (wire), the needle is deflected. This shows that a conductor carrying current has a magnetic field around it.
If the direction of the current is from north to south, the deflection of the magnetic needle is towards the east.
If the direction of the current is from south to north, the deflection of the needle is towards the west.
The magnetic field around a current carrying straight conductor is in concentric circles. It can be observed by passing a current carrying straight conductor through a cardboard and sprinkling iron filings on it.
N
N
S
S
W
E
Right hand thumb rule:-
The direction of the magnetic field around a conductor is given by the Right Hand Thumb Rule.
It states that ‘ If a current carrying conductor is held in the right hand such that the thumb points in the direction of current, then the fingers wrapped around the conductor shows the direction of the magnetic
field .’
Magnetic field due to a current through a � circular loop :-
When current is passed through a circular conductor (loop) the magnetic field produced is in the form of concentric circles around the conductor. Towards the centre the arcs of the circles become larger and appears as straight line.
Magnetic field due to current in a solenoid :-
A solenoid is a circular coil of wire in the shape of a cylinder.
When current flows through a solenoid, it behaves like a bar magnet. The ends of the solenoid behaves like the North and South poles of a magnet. The magnetic field produced by a solenoid is similar to the magnetic field produced by a bar magnet.
The strength of the magnetic field depends upon the strength of the current and the number of turns of the coil.
Electromagnet :-
A strong magnetic field inside a solenoid can be used to magnetise a piece of magnetic material like a soft iron when placed inside the coil. Such a magnet is called an electromagnet.
If electric current is passed through a wire wound around a piece of soft iron, it behaves like a magnet. Such a magnet is called an electromagnet.
( )
Force on a conductor carrying current in a magnetic field :-
A.M.Ampere suggested that if a current carrying conductor produces a magnetic field and exerts a force on a magnet, then a magnet should also exerts a force on a current carrying conductor.
Eg :- If an aluminium rod is suspended horizontally by a wire between the poles of a horse shoe magnet and current is passed through the wire, then the aluminium rod is displaced. If the direction of current is reversed, the direction of displacement is also reversed. The force exerted is maximum if the conductor is perpendicular to the magnetic field.
Fleming’s Left Hand Rule :-
The direction of force (motion) of a current carrying conductor in a magnetic field is given by Fleming’s Left Hand Rule.
It states that ‘ If we hold the thumb, fore finger and middle finger of the left hand perpendicular to each other such that the fore finger points in the direction of magnetic field, the middle finger points in the direction of current, then the thumb shows the direction of force (motion) of the conductor’.
Electromagnetic induction:- (Michael Faraday)
The motion of a magnet with respect to a coil or a change in the magnetic field induce a potential difference in the coil and produces induced current. This is called electromagnetic induction.
i) Motion of a magnet with respect to a coil produces induced
current :-
If a magnet is moved towards or away from a coil of wire connected to a galvanometer, the galvanometer needle shows a deflection. This shows that current is induced in the coil due to the motion of the magnet.
ii) Change in magnetic field produces induced current :-
Take two coils of wires wound around a cylindrical paper roll. Connect one coil to a battery and the other coil to a galvanometer. If current is passed through the first coil, the galvanometer needle shows a deflection in the second coil. If the current is disconnected, the needle moves in the opposite direction. This shows that current is induced due to change in magnetic field.
Coil -1 Coil - 2
( )
battery key galvanometer
Fleming’s Right Hand Rule :-
The direction of induced current is given by Fleming’s Right Hand Rule.
It states that ‘ If the thumb, fore finger and middle finger of the right hand is held perpendicular to each other such that the thumb points in the direction of motion of the conductor, the fore finger points in the direction of the magnetic field, then the middle finger shows the direction of induced current ’.
Direct and Alternating current :-
a) Direct current (DC) :- A current that always flows in one direction
only is called direct current.
The current we get from a battery is a direct current.
b) Alternating current (AC) :- A current that reverses its direction
periodically is called alternating current.
Most power stations in our country produce alternating current. AC
changes direction every 1/100 second and its frequency is 50 Hertz
(Hz).
One advantage of AC over DC is that it can be transmitted over long
distances without much loss of energy.
Direct current Alternating current
Current Current
0.01s 0.02s 0.03s
Time (s)
Time(s)
FIXED DOME TYPE BIOGAS PLANT
BOX TYPE SOLAR COOKER
Mirror reflector
Glass plate
Insulated box
Painted black
inside
Containers
Painted black
outside