Physics Practical explores fundamental concepts in electricity, including electric current, potential difference, and resistance. It provides detailed experiments to study Ohm’s Law and the behavior of resistors in series and parallel circuits. This practical guide is essential for students in physics courses, offering hands-on activities to reinforce theoretical knowledge. It includes step-by-step methods, observations, and calculations to help students understand the principles of electricity. Ideal for high school and college-level physics students preparing for exams.

Key Points

  • Explains electric current and its measurement in amperes.
  • Covers experiments on potential difference and resistance using Ohm’s Law.
  • Includes practical applications of resistors in series and parallel circuits.
  • Provides step-by-step methods for conducting physics experiments.
Prem Kumar
9 pages
Language:English
Type:Lab Report
Biology
Prem Kumar
9 pages
Language:English
Type:Lab Report
Biology
334
/ 9
5
ELECTRIC
CURRENT,
P0TENTIAL
DIFFERENCE
AND
RESISTANGE
Experinent
Introduction...
The
flow
of
free
electrons
in
a
definite
direction
in
a
conductor
constitutes
an
electric
Current.
The
rate
of
flow
of
charge
through
a
conductor
is
called
electric current.
Current
(1)
-
Charge(q)
Time(t)
The
SI
unit
of
electric
current
is
ampere
(A).
AIM:
To
study
the
dependence
of
potential
difference
(V
across
a
resistor
on
the
current
()
passing
through
it
and
to
determine its resistance. Also plot a graph between Vand
Theory
The
current flowing through a conductor
is
said
to
be 1 ampere when 1 coulomb
of
charge
flows
through a
conductor
in 1
second.
The
amount
of
work
done
when
a
unit
charge
flows
from
one
point
to
another
point
in
an
electric
circuit
is
called
potential
difference
(p.d.).
The
S/
unit
of
p.d. is volt (V).
The
maximum
p.d.
which
can
exist
between
two
terminals
of a cell, whern
no
current
is drawn from
the
cell
is
called its
electromotive
force.
The
S/
unit
of
e.m.f. is volt
and
the
instrument
used
for
measuring
e.m.f. or
p.d. is
called
voltmeter.
When
a conductor
opposes
the
flow
of electric current through
it,
it
is
called resistance. The
SI
unitof
resistance
is
ohm
(2).
The
resistance
of
a
conductor
is
said
to
be
1
ohm
if
p.d.
of
1
volt
is
developed
across
its
ends
when
a
current
of
1
ampere
flows
through
it.
The
resistance
of
a
conductor.
depends
upon:
1.
Nature
of
the
conductor
2.
The
length
of
the
conductor
(more
the
length
more
the
resistance),
3.
The
area
of
cross-section
of
the
conductor
(more
the
area
of
cross-section,
less
is
the
resistance).
he
resistance
of
pure
metals
generally
increases
with
the
rise in
temperature.
Materials
like:
Nichrome,
constantan,
manganin
are
usually
used
for
making
resistors,
as
their
resistivities
are
constant
over a wide range of temperatures.
Ohm's
law
states
that:
Ihe
electric
current
flowing
through
a
conductor
is
directly
proportional
to
the
potential
difference
across
Its
ends,
provided
that
physical
conditions
like
temperature,
pressure,
area
of
cross
section,
etc.
remains
constant.
Voc
I,
where
V=
p.d.
and
I
=
current
or
V
RxI,
where
R
is
constant
called
resistance
of
the
conductor
or
R
LAB
Manual-X
39
If
we
plot
a
graph
between
different
values
of
current
and
current
and
corresponding
values
of
voltage,
the
graph
will
be
a
straight
line.
We
can
obtain
the
resistance
of
the
conductor
in
the
circuit
by
calculating
the
slope
of
the
V-I
graph,
that
is,
8
ReAV
AV
R slope
of
V-
Igraph
AV
MATERLALS
REQUIRED:
10
pieces
of
thick
insulated
copper
wire with
bare
ends,
pieces
of
sand
paper,
one-way
key, a dry cell with (+)
and
(-)
terminals,
an
ammeter
(of
range
0-1.5
A),
a
voltmeter
(of
range
0-1.5
V),
a
rheostat
(10
2),
a
resistor
(of
about
2
2
resistance).
Current
()
in
ampere
Figure. 5.1
VI
graph
to
calculateR
METHOD:
1.
Usinga
sand
paper,
clean
the
ends
of
the
connecting
wires.
2.
Remove
the
plug
from
the
one-way
key
K.
3.
Connect
the
key,
the
rheostat,
the
ammeter
and
the
resistor
in
series
with
the
connecting
wires
to
the
dry
cell
and voltmeter
in
parallel
to
the resistor.
4.
Insert
the
plug
in
the
key.
Check
if
the
ammeter
and
voltmeter
show
deflection.
There
should
be
deflection
in
both.
5.
Adjust
the
slider
of
the
rheostat,
such
that
the
ammeter
shows
a
current
of
0.10
A
and
note
the
corresponding
value
of
potential
difference
from
the
voltmeter.
one-way
key
rheostat
6.
Take
out
the
plug
from
the
key.
Note
the
values
of
current
and
potential
difference
in
the
table
7.
Replace
the
plug
in
the
key.
Adjust
the
slider
of
the
rheostat,
such
that
the
ammeter
shows
battery
a
current
of
0.20
A.
uniform
resistance
8.
Note
the
values
of
curent
and
potential
WWw
difference
in
the table.
*********-**
**.
9.
Repeat
the
experiment,
by
adjusting
the
slider
a
few
times,
for
the
values
of
current
0.30
A,
0.40
A,
0.50
A
and
0.60A.
10.
Note
the
corresponding
potential
difference
in
ammeter
the
table.
voltmeter
RESULT:
Figure. 5.2 Arrangement
diagram
Mean
resistance
of
the
resistor
=
ohms
Resistance
of
Resistor
A
in
ohms
No.
Current
in
Amperes
(1)
P.D.
in
Volts
(V)
(R)=
V
1.
2.
3
4.
5.
6.
Plot
a graph
between
Vand
I by taking potential difference
(V)
on y-axis
and
current
()
on
xX-axis.
Join all
points
by
a
line.
**-+_
CONCLUSION:
1.
We
can
see
in
the
table
that
the
ratio of V
and
Iis
constant. So,
it
is verified
that
potential difference is
directly
proportional
to
current
flowing
in
the
circuit
2.
The
resistance
R
of
a
conductor
is
equal
to
the
ratio of potential difference V to current I.
3. As
the
graph
is a
straight
line,
it
proves
that
Vis
directly proportional to I.
4.
The
slope
of
the
graph
is
the
magnitude
of
resistance.
This verifies
Ohm's
law.
PRECAUTIONS
1.
The
zero
error
in
the
ammeters
and
voltmeters should
be
corrected by adjusting
the
zero
adjustment
screw.
2.
Insert
the
plug
key
just
before
you
are
ready
to
record
the
reading
and
remove
the
plug
key
as
soon
as
have
finished
taking
your
reading
3.
All
connections
should
be
neat
and
tight.
4.
The
value
of
the
resistance
is
likely
to
be
wrong,
if
the
connections
are
not
tight
or
the
ends
of
copper
wires
are
not clean.
5.
Use
a
low
resistance
rheostat
(not
more
than
10
ohm
resistance).
6.
Positive
terminals
of
the
ammeter
and
of
the
voltmeter
should
be
connected
to
the
positive
terminal
of
the cell
in
the
circuit.
7.
Keep
the
value
of
current
through
the
circuit
as
low
as
possible
to
avoid
heating
of
the
resistor.
t
LAB
Manual-X
41
/ 9
End of Document
334

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FAQs

What is the definition of electric current in this lab report?
Electric current is defined as the flow of free electrons in a definite direction through a conductor. The rate of flow of charge through a conductor is called electric current, measured in amperes (A). It is quantified using the formula Current (I) = Charge (q) / Time (t).

How is potential difference defined in the document?
Potential difference, or p.d., is defined as the amount of work done when a unit charge flows from one point to another in an electric circuit. The SI unit of potential difference is the volt (V). The maximum potential difference that can exist between two terminals of a cell, when no current is drawn, is referred to as electromotive force (e.m.f.).

What does Ohm's Law state according to the lab report?
Ohm's Law states that the electric current flowing through a conductor is directly proportional to the potential difference across its ends, provided that physical conditions such as temperature and pressure remain constant. This relationship can be expressed mathematically as V = I × R, where V is the potential difference, I is the current, and R is the resistance.

What materials are required for the experiment on electric current and resistance?
The materials required for the experiment include 10 pieces of thick insulated copper wire with bare ends, sandpaper, a one-way key, a dry cell with positive and negative terminals, an ammeter (0-1.5 A range), a voltmeter (0-1.5 V range), a rheostat (10 ohm), and a resistor of about 2 ohms resistance.

How do you calculate the resistance from the V-I graph?
To calculate the resistance from the V-I graph, you plot the potential difference (V) on the y-axis and the current (I) on the x-axis. The graph will be a straight line, and the resistance can be determined by calculating the slope of this line, represented by the formula R = ΔV / ΔI, where ΔV is the change in potential difference and ΔI is the change in current.

What precautions should be taken during the experiment?
Precautions include correcting any zero error in the ammeter and voltmeter, ensuring that connections are neat and tight, and using a low resistance rheostat (not more than 10 ohms). Additionally, the positive terminals of the ammeter and voltmeter should be connected to the positive terminal of the cell, and the current should be kept low to avoid heating the resistor.

What is the significance of the slope of the V-I graph?
The slope of the V-I graph represents the magnitude of resistance in the circuit. Since the graph is a straight line, it confirms that the potential difference is directly proportional to the current flowing in the circuit, thereby verifying Ohm's Law. A constant slope indicates that the resistance remains unchanged under the experimental conditions.