4. Electric Charge is the property of subatomic
particles that causes it to experience a force
when placed in an electric and magnetic field.
It can be : positive (by protons) and also
negative (by electrons)
5. Elementary Charge :
The charge of a single electron or proton is known
as elementary charge.
1 proton =
1 electron =
The total charge acquired by a body is an integral
multiple of magnitude of charge on a single
electron. This is called as Quantisation of Charge.
6. ● An object with an absence of net
charge is referred to as neutral.
● But we can change that by causing an
atom to gain or lose electrons.
7.
8. Law of Conservation of
Electric Charge :
States that charge can neither
be created nor be destroyed. It
can only be transferred from
one object to another.
9. Electric Current :
is the movement of charge in a wire over
a period of time.
Symbol = I
Unit = Ampere (A)
10. A current of 100A flows through a circuit for 2
minutes. Find the amount of charge that flows
through the circuit?
11. A total of 6 X 1046
electrons flow through a current
carrying conductor when connected through an
external power supply for 10 seconds. Find the
value of current in the conductor.
12. Prerequisites for a current to flow :
● Conductor
● Energy Source (cell or battery)
● Switch (on/off)
15. Potential Energy : is the energy possessed
by an object by virtue of its position.
16.
17. Electric Field :
It is a force field around a charged object
that illustrates the direction the electric force
would push an imaginary positively charged
particle.
18. Electric Potential energy : is thus the energy that
is needed to move a positive charge from infinity
to a point which is then stored in that positive
charge.
Electric Potential :
IT IS THE AMOUNT
OF WORK DONE
WHEN A UNIT
POSITIVE CHARGE IS
MOVED FROM
INFINITY TO A
POINT.
Detonated by V (volt).
Named after Italian
physicist Alessandro
Volta. It is a scalar
quantity.
19. Electric Potential Difference :
Imagine you move a positive charge first to
point A (having a voltage V1) and then to point B
(having a voltage oV2). How will you calculate
the work done in moving it from point A to B?
Well, you can!
This is called as Electric Potential Difference :
EPD between two points is defined as the work
done in moving a unit positive charge from one
point to other point.
20. How much work is done in moving a charge of 5 C
across two points having a potential difference
of 10 V?
21. A charge of 10C was moved from one terminal of a
battery to another. In doing so 200 J of work was
done. Calculate the potential difference between
these two terminals
22. Calculate the work done in moving a charge of 4 C from a point at 220 V to a
point of 230 V
23. Electric Circuit :
It is a closed and continuous path
through which electric current flows.
24.
25. Ohm’s Law :
Electric current flowing through a conductor
is directly proportional to the potential
difference across its ends provided the
physical conditions remain unchanged.
26. For practical purposes, resistors (such as
rheostats) are connected to the circuits to
regulate current. Rheostats have variable
resistance and thus impact the current, as :
I = V/R
27. But even conductors have some resistance as the
electrons in them are not totally free to move.
They are restrained by the attractions of the
atoms.
29. Resistivity : It is defined as the resistance
of a conductor of unit length and unit area
of cross section.
Unit = ohm-metre
Also known as :
● Electric Resistivity
● Specific resistance of the material of
the conductor
31. Cons of series combination:
1. In this, if any of the component fals to
work, the circuit will break.
2. Not possible to connect a bulb and a
heater simultaneously as they need
different value of current.
3. Not practical for household circuits.
32. Resistors in Parallel combination: are
connected simultaneously between 2 points
to each other.
33. Application of parallel combination:
1. Useful in household circuits
2. Divides the current for different
gadgets
34. A metal wire has diameter of 0.25mm and
electrical resistivity of 0.8 X 10-8
ohm-meter.
a) What will be the length of this wire to make
a resistance 5 ohm
b) How much will the resistance change if the
diameter of the wire is doubled?
36. A student carries out an experiment and plots the V-I graph of three samples of
nichrome wire with resistances R1, R2 and R3 respectively (Figure.12.5). Which of the
following is true?
39. Two lamps one rated 100W - 220V and other 60W -
220V are connected in parallel to electric mains
supply. What current is drawn from the line, if
supply voltage is 220 V?
41. Electric Power : is defined as the amount of
electric energy consumed in a circuit per unit
time.
It W is the amount of electric energy consumed
in a circuit in t seconds, then electric power
would be :
42.
43. If the current I through a resistor is increased by
100% (temp unchanged), how much would be the
increase in power :
a) 100%
b) 200%
c) 300%
d) Unchanged
44. An electric lamp of resistance 20 ohm and a conductor of resistance 4
ohm are connected to a 6 V battery as shown in the circuit.
i) The total resistance of the circuit
ii) The current through of the circuit
ii) The potential difference across the ELECTRIC LAMP
iv) The power of the lamp
45. An electric lamp of resistance 20 ohm and a conductor of resistance 4
ohm are connected to a 6 V battery as shown in the circuit.
i) The total resistance of the circuit
ii) The current through of the circuit
ii) The potential difference across the ELECTRIC LAMP
iv) The power of the lamp
46.
47. Heating effects of current : A bulb
It has a filament made up of tungsten.
Tungsten has a high resistivity and a even
higher melting point.
The filament is thermally isolated as much
as possible, using insulating support, etc.
The bulbs are usually filled with chemically
inactive nitrogen and argon gases to
prolong the life of filament.
Most of the power consumed by the filament
appears as heat, but a small part of it is in
the form of light radiated.
48. Heating effects of current : Electric Fuse
Fuse is used in electric circuits. It protects
circuits and appliances by stopping the flow of
any unduly high electric current. The fuse is
placed in series with the device.
It consists of a piece of wire made of a metal or
an alloy of appropriate melting point, for
example aluminium, copper, iron, lead etc.
If a current larger than the specified value
flows through the circuit, the temperature of the
fuse wire increases.
This melts the fuse wire and breaks the circuit.
The fuse wire is usually encased in a cartridge
of porcelain or similar material with metal ends.
The fuses used for domestic purposes are rated
as 1 A, 2 A, 3 A, 5 A, 10 A, etc.
