If you are a student preparing for exam, this is for you or maybe
you are a teacher trying to refresh your brain before going to class, this is
also very useful to you.
This physics practical on electricity is going to teach you the relationship between resistance, current and potential difference as stated by ohms law.
Let take it that the circuit is connected as shown above. In this circuit you are to determine the
current as we vary the resistance in the resistance box.
Take e.m.f of the battery as 1.5V for this physics practical
Set the resistance at the resistance box to R=OΩ
Close the key and
Read the current I, at ammeter A in the circuit above
Repeat the procedure with R2, R3, R4 , R5 R6,
This is done by adjust resistance in resistance box to R1,
R2, R3, R4,
R5 and R6 and obtaining the corresponding I1, I2, I3, I4, I5
and I6 from ammeter A reading ,respectively .
Record the value of R1,
R2, R3, R4, R5 and R6
Record the value of current I1, I2,
I3, I4, I5 and I6
After this you are done with you physics practical on
electricity, what is remaining is the follow up questions
Let assume that the reading of resistance and the current are represented by the diagrams below
In above diagram the active resistance is the one that is
not painted while the painted one is not active.
Therefore from this diagram, resistance R1 = o, R2 =1, R3 = 2 R4 = 3, R5 = 4 and R6 = 5.
From the diagrams above you can take your reading and make a
table as shown below
Reading from the diagram above shows that, I1= 3.00, I2.00 =1, I3 =0.60, I4= 043, I5=0.33, and I6 =0.27
NOTE: When you
are writing experimental value put it in two
decimal places, If it is a worked value, it can be in three decimal place. And
also note that, they must be in uniform decimal places, so you cannot put one in two decimal places, and the other in three
From what we got from resistance box and the Ammeter we can make this table below.
Follow up questions
on physics practical electricity
1. Evaluate P =E/I and make a table of I, R, and p
2. State the precaution you would have used if you were
performing this experiment in laboratory
3. Define the internal resistance of the cell
4. A cell of e.m.f 4.5V is connected across a resistor of resistance 4Ω. If a current of 0.9A passes through the circuit, calculate the internal resistance of the cell.
Answers to the follow
up question on the physics practical electricity
1. P= E/I
When E =1.5
and I 0.27, p = 1.5/0.27 =6.o
2. Precautions used in physics practical on electricity above.
(a) I made sure that the key is removed or not closed when I
was not taking the reading
(B). I ensured tight connections
(C) I ensured that the terminals are clean before connection
(D). I avoided the zero error of ammeter.
Please while listing the precautions, do not use present or
future tense, but use past tense as I did above. Fellow to do that may attract no
mark or penalty.
3. Definition of internal resistance
Internal resistance is the resistance of cell when is not
delivering any current. Or opposition to the flow of current offered by the
4. Calculation of internal resistance when, e.m.f of the
cell is 4.5V, resistance = 4Ω, and the current =0.9A
Using I = E/R + rwhere r = internal resistance, therefore