class 10 cbse science physics Electricity

1. ELECTRICITY
class – 10 (CBSE)
Aditya Mishra
Email: adityakumar2009@gmail.com
Calendula Learning

2. Potential difference (V) :
• Work done to move electrical charges from a point at high
electric potential to a point at low electric potential per unit
total charge
AB
W
V =
Q
(Volt)
-
W
=
n e

- -
-
-
-
-
-
-
-
-
-
-
-
A
B
VA VB
(8e-)
Work done
Definitions
Calendula Learning

3. -
Q = n e

1. Total charge (Q) :
2. Electric current (I) :
• Total electric charge flowing through any given cross section area
of conductor in unit time
-
Q n e
I =
t t


Where, n = total number of electrons
e = charge on each electron
(coulomb, C )
(ampere, A)
Calendula Learning
Definitions

4. Q.1 How many electrons are needed to create a total charge of 1 C ?
Q = 1 C
n = ?
Given :-
To find :-
Solution :-
-19
= 1.6 10
e C

We know that
Q = n e

Q
n =
e

-19
1
=
1.6 10

+19
= 0.625 10

+16
n = 625 10

625,000,000,000,000,000 electrons
Examples
Ans :
Calendula Learning

5. Q.2 How many electrons should be allowed to flow through the
wire in order to create a current of 1 ampere in one time?
I = 1A
-19
e = 1.6 10 C

t = 1s
n = ?
Given :-
To find :-
Solution :-
Q
I =
t
Q n e
I =
t t


I t
n =
e

-19
1× 1
=
1.6 × 10
+19
1× 10
=
1.6
( Q= n e)

+19 +19
10
= 10 0.625 10
16
  
16
n = 625 10

Ans :
Examples
Calendula Learning

6. Q.3 A current of 1 ampere is passed through the conductor for 1
min. Calculate the total charges passing through any given
cross section area?
I = 1A
t = 1 min
Q = ?
Given :-
To find :-
Solution :-
Q
I =
t
Q = I t
 
= 1 60
= 60 C

= 60 s
By definition electric current
Q = 60 C

Total charge,
Ans :
Examples
Calendula Learning

7. Electric circuit :
• A closed and continuous path through which the current flow
(electrons move) is called an electric circuit.
Current
Direction of flow of electron
• Electric current always flows from positive to negative terminal of cell
DEFINATIONS
Calendula Learning

8. 1Volt (V):
• Potential difference between two points is said to be 1 volt
when 1Joule of work is done to move 1C of electrical
charge through any given cross section of the conductor
W 1 Joule
V =
Q 1 coulomb

1 ampere (A):
• Electric current flowing through wire is said to be of
1 ampere when 1 C of electric charges flow through the wire
in one second (unit time)
Q 1 coulomb
I =
t 1 second

DEFINATIONS
Calendula Learning

9. Ohm’s Law :
• As long as physical state of the conductor remains the same
(temperature remains constant )
• Potential difference applied across the ends of wire is directly
proportional to the current flowing through it
Potential difference electric current

V I

V = constant I
V = R I
V = I R
Where R = resistance ,
= property of material of wire
OHM’S LAW
Calendula Learning

10. Current , I ( Ampere)
Voltage
,
V
(
Volt
)
2 1
2 1
Slope of line =
y y
x x


2 1
2 1
V - V
=
I - I
slope of V vs I graph = Resistance
V I

• Straight line passing through the origin
V - 0
=
I - 0
V
= R
I

Calendula Learning
DEFINATIONS

11. Current , I ( Ampere)
Voltage
,
V
(
Volt
)
A
B
C
RA > RB > RC
Slope A > Slope B > Slope C
Calendula Learning
DEFINATIONS

12. 0
2
4
6
8
10
0 1 2 3 4 5
Voltage
,
V
(
Volt
)
Current , I Ampere)
3 2
3 2
Resistance = slope of the line
V - V
=
I - I
4 - 3
=
2 - 1
( V3, I3)
( V2, I2)
1
=
1
Resistance = 1 
OHM’S LAW
Calendula Learning

13. 1. Does this graph obey ohm’s law ?
2. What happens to the resistance of the
conductors with increases in current ?
3. Calculate the resistance of the wire ?
0.00
2.00
4.00
6.00
8.00
10.00
0 1 2 3 4 5
Potential
difference
(Volt)
Current ( amperes)
HOME ASSIGNMENT
Q. Look at the following graph and answer the following questions :
Calendula Learning

14. 1. What is resistance ?
2. What are the factors affect the resistance of the
conductor ?
3. How can the resistance of a conductor be changed?
4. What is SI unit of resistance? What is the reciprocal
of resistance called ?
RESISTANCE
Calendula Learning