Physics Class X Electric Current Contents 1 Electricity 2 Electric Current 3 Electric Potential & Potential Difference 4 Electromotive Force (emf) 5 Electric Circuit and components 6 Current and Voltage Measurements 7 OHM’s Law 8 Factors Affecting Resistance 9 Combination of Resistors(Series & Parallel) 10 Heating Effect of Electricity and its apps.

2. i. Electricity
ii. Electric Current
iii. Electric Potential & Potential Difference
iv. Electromotive Force (emf)
v. Electric Circuit and components
vi. Current and Voltage Measurements
vii. OHM’s Law
viii. Factors Affecting Resistance
ix. Combination of Resistors(Series &
Parallel)
x. Heating Effect of Electricity and its apps.

3. Electricity is a form of a energy that can be
easily changed to many other forms

4.  Electric Current is the flow of electric charge
 Measured as the rate of flow of electric
charge
 Denoted by I
 I=Q/t
 SI unit -> Amperes(A)
NOTE-Direction of CONVENTIONAL Current is opposite to direction of flow of electrons.

5. Electric Potential - Work done in moving a unit charge
from infinity to a point
.∞
A .
Potential Difference – The difference between
potential at two points
.∞
B. A.
Potential difference

6. Final GPE
Initial GPE
Potential
Difference

8. pd

10. Electromotive force is the same as
voltage.
E.m.f refers to the amount of energy
supplied by the electric source (eg.
battery) to each unit of electric charge
E.m.f is also measured by a voltmeter

11. To make an electrical appliance work,
electricity must flow through it.
The path along which the electric
current moves is called the electric
circuit.

12. Component Symbols – a cell
• The cell stores chemical
energy and transfers it to
electrical energy when a
circuit is connected.
• The long line is the positive end
• The short line is the negative
end

13. Battery
• When two or more cells
are connected together
we call this a Battery.
• The cells chemical
energy is used up
pushing a current
round a circuit.
• It is important that each
cell faces the right way

14. Switch
• A switch can be open (as
shown) or closed
• When the switch is
open, the circuit is
incomplete – no
electricity can flow

15. Bulb / Lamp
• The lamp lights up
when electricity
flows through it

16. Wires
The wires which carry electricity consist of two parts:
• The metal wires (conductor).
• The plastic coating around the metal wires (insulator).
• Prevents people from being electrocuted.
wires

17. Resistor
• A resistor can change the amount of current in a
circuit
• In a variable resistor, the resistance can be changed.

19. Fuse
• A fuse is a safety
device
• When the current
is too high, the
fuse breaks
Example
The wire inside a 3A fuse will melt when the current is greater
than 3A.

20. Circuit Symbols
Voltmeter
Ammeter
Variable Resistor
Switch
Bulb
Motor
Cell
Battery

21.  It must be connected in series in the circuit.
 Positive side of ammeter must be connected
nearest to the positive terminal of the battery
(electric cell), and vice versa.

22.  Voltmeters must be connected in parallel to
the circuit.
 The positive side of voltmeter is connected
to the positive terminal of the cell, and vice
versa.

23. At constant temperature, Current flowing
through a conductor is directly
proportional to potential difference
across its ends
V∝I
V/I = Constant
= R
V =IR
R -> Ressiatance (Ω or ohm)

24.  Fixed resistors have only one
resistance value
 Variable resistors can be adjusted
to change the resistance,
example- Rheostat
Fixed Resistors Rheostat

25. Length of Conductor ->> R∝l
Cross-sectional Area of conductor ->> R ∝ 1/A
Nature of material of conductor
Temperature of conductor
R∝l/A
ρ – Constant of proportionality called Resistivity
Unit of Resistivity – Ωm
Metals and Alloys have very low resistivity whereas
insulators have very high resistivity
R= ρl/A

26. Thereare 2 ways of joining
resistors together
a) Series
b) Parallel

27. The components are connected end-to-end, one
after the other.
They make a simple loop for the current to flow
round.
SERIES CIRCUITS
If one bulb ‘blows’ it breaks the whole circuit and
all the bulbs go out.

28. PARALLEL CIRCUITS
The current has a choice of routes (paths).
The components are connected side by side.
If one bulb ‘blows’ there would still be a complete circuit
to the other bulb so it stays lit.

29. Measuring current
Electric current is measured in amps (A) using
an ammeter connected in series in the circuit.
A

30. Measuring current
A A
This is how we draw an ammeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUIT

31. Measuring current
SERIES CIRCUIT
PARALLEL CIRCUIT
• current is the same
at all points in the
circuit.
6A 6A
6A
• current is shared
between the
components
4A4A
3A
1A

32. Fill in the missing ammeter readings.
?
?
4A
4A
4A
3A?
?
1A
?
3A
1A
1A

33. Measuring voltage
The ‘electrical push’ which the cell gives to the current
is called the voltage. It is measured in volts (V) on a
voltmeter
V

34. Different cells produce different voltages.
The bigger the voltage supplied by the cell, the bigger
the current (the cell gives a bigger push to the
electrons).
measuring voltage

35. Measuring voltage
Unlike an ammeter a voltmeter is connected across
the components (in parallel)
Scientist usually use the term Potential Difference
(pd) when they talk about voltage.

36. Measuring voltage
V
This is how we draw a voltmeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUIT
V

37. V
Measuring voltage
V
V
V

38. Series circuit
1.5V
• voltage is shared between the components
1.5V
3V

39. • voltage is the same in all parts of the circuit.
3V
Parallel circuit
3V
3V

40. Measuring current & voltage
V V
6V
4A
A
A
a)

41. Measuring current & voltage
V
V
6V
4A A
A
A
b)

42. Answers
3V 3V
6V
4A 4A
6V
6V
6V
4A 4A
2A
2A
4A
a) b)

43. When an electric current flows through a wire,
the wire heats up. Electrical energy has been
converted into heat energy.
The greater the resistance of the wire, the
greater the amount of heat produced. This
heating effect is used in common electrical
appliances.
Iron Kettle

44.  The work done in moving the charge Q through a potential
difference V is VQ
 Therefore, the source must supply energy equal to VQ in time t.
 So, power input to the circuit by the source is
P = V(Q/t)
P=VI
Energy supplied to the circuit by the source in time t is
P × t
orH= VIt H=I²Rt

45. filament wire produces
heat and light
In a light bulb, the heated filament
which is also a resistance wire,
becomes so hot that light is also
emitted.

46. A kettle uses both copper and nichrome wires.
Copper has low resistance while nichrome has high resistance.
Which material, copper or nichrome, should be used for the heating
element, and for the external wire?
Use copper wire
for the external
wire as it has low
resistance &
produces less heat
Use nichrome wire for the heating
element as it has high resistance&
produces a lot of heat

47. Summary
 Uses of electricity in our daily life
 Sources of Electricity (Main electricity and
electric cells)
 Define electric current and electric circuit
 4 different parts of circuits and their symbols
• Connecting wires
• Bulbs
• Switch
• Electric cell

48. Electric Current
• Positive and negative
• Pushes electrons out of the
negative terminal and round the
circuit
• Flow back to the positive terminal
of the cell
• Electrons are not used up only
energy is used up

49. What is Voltage?
• To measure the energy the electrons
receive
• An electron can have a large amount
of potential energy at one point in the
circuit
• It can also have a low amount of
potential energy at another point
• The difference in potential energy
between the two points is known as
voltage

50. What is a resistor?
• Appliances need to ensure that
the correct size of current flows
to operate properly
• To control the size of the current,
electrical components called
resistors are used in the circuits

51. Arrangement of resistors
• Parallel
– For resistors in parallel, current
from the electric cell divided among
the resistor
– More resistors added more
electrical charges are able to flow
through the resistors at the same
time
– Current in circuit increases
– Overall resistance of the parallel
circuit decreases

52. Heating Effect
• Resistance in circuit wires affects
the amount of electric current
flowing
• Electric current flows through the
wire, the wire gets heated up
• Electrical energy to heat energy