DC Power Sources and Ohm’s Law
Andrea Allen L. Lu Malayan Colleges Laguna
[email protected] ABSTRACT
DC Power sources could be in parallel or series connection. Battery is considered as the most basic source of electricity electricity known by everyone. Before there is no definite way in predicting the change of current if voltage and resistance has been altered, however, this has been solved by Georg Simon Ohm. By using DC fundamental circuit board, concepts about Ohm’s law will be understood. understo od. At the end of the experiment it was concluded that cells connected in series increases the voltage output and cells connected in parallel increases the current capability.
and the voltage drop across each resistor is the sum of all voltage drop is equal to the voltage source as shown in Eqn. 3 = 1 + 2 + ⋯ +
(3)
In a parallel circuit, the current across each resistor is the sum of all current flowing as shown in Eqn. 4 (4)
= 1 + 2 + ⋯ +
and the voltage drop across each resistor is equal with the voltage source as shown in Eqn. 5
KEYWORDS
(5)
= 1 = 2 =
Battery, Voltage, Current, Resistance, Series, Parallel
Table 1.
1 INTRODUCTION
Relationship of voltage, current and resistance has been defined by Georg Simon Ohm as stated in Eqn. 1 =
(1)
The voltage has a direct relationship with current and resistance. There are two types of circuit connection, namely, series and parallel connection. A circuit is considered in a series connection when the current flows in a sequential manner. Then a circuit is considered in a parallel connection when the each resistor is directly connected to the power source (OpenStaxCollege, n.d.). In a series circuit, the current across each resistor is equal with one another as shown in Eqn. 2 = 1 = 2 =
2 RESULTS
(2)
DC Power Sources in Series and in Parallel
Description Measure: V1 V2 Calculate: VT Measure: VT Compare VT Measure: V3 V4 Using two-post connector measure: V3 V4 Compare the measured V3 and V4 Switch that causes LED to be brighter
Result 1.3V 1.5V 2.8V 2.9V Different 1.5V 1.5V
1.5V 1.5V Same S1
Observing the results from table 1, V1 and V2 are in series connection due to difference
in voltage drop while V3 and V4 are in parallel connection for they have the same measured voltage drop. Table 2.
Series-Opposing DC Sources
Description
Potential difference is 0V LEDs Supply control adjusted CW measure: V5 V6 Potential difference Supply control adjusted CCW measure: V5 V6 Potential difference Brightest LED when control is at: CW position CCW position Table 3.
5.53V -27.8 mV
5.54V 1.504V -4.63V 5.68V V5 at 5.54V V6 at 0.903V to 11.22V
Off
5.54V 7.48V 1.95V
5.54V 3.55V -1.98V
LED B LED A
Band 2
Brow n Brow n Gold
Result
R1
Band 4 Record values of: R1 R2 Measure: R1 R2 R T Are the resistors within tolerance Measure: IT Measure voltage drop: V1 V2 Calculate: R1 R2 Compare the color code and calculated resistance Measure IT when switch 19 is on Calculate: R T Measure IT when switch 20 is on Calculate: R T Measure voltage drop: V1 V2 Calculate: R1 R2
Brow n Black Red Gold
510 5% 1000 5% 0.506 kΩ 0.975 kΩ 1.482 kΩ Yes 6.76 mA 3.421 V 6.58 V 506.065 Ω 973.373 Ω Same 2.73 mA 3663 Ω 8.28 mA 1207.729 Ω 2.018 V 8.03 V 243.7198 Ω 969.8068 Ω
Other than computing the resistance through Ohm’s law, color codes is one way in determining the value of resistance a resistor have as shown in table 3.
Ohm’s Law - Circuit Resistance
Description Record the color codes of the two resistor:
Green
Band 3
Result
Measure: V5 Potential difference at V5 and V6 Measure when PD= 4V: V5 V6 Potential difference: VCCW VCW Remains constant Varies
Band 1
R2
Table 4.
Ohm’s Law - Circuit Current
Description Measure: R T Calculate: IT Measure: IT Compare the calculated and measured IT Calculate IT at 5V Measure: IT Compare the calculated and measured IT Measure R T when switch 20 is on Calculate: IT Measure: IT Compare the calculated and measured IT
Result 1.486 kΩ 6.729 x 10-3 A 6.81 x 10-3 A Nearly the same 3.3647 x 10-3 A 3.38 x 10-3 A Nearly the same 1.219 kΩ 8.203 x 10-3 A 8.24 x 10-3 A Nearly the same
Observing the values of the measured IT with the calculated IT, it could be seen that they almost have the same value as shown in table 4. Table 5.
Ohm’s Law - Circuit Voltage
Description Record: R T Calculate: VT Measure: VT Compare the calculated and measured VT Calculate: V1 V2 Measure: V1 V2 Compare the calculated and measured voltage drop Measure IT when switch 19 is on Compare the IT Measure: R T
Result 1510 Ω 5.5568 V 5.49 V Nearly the same 1.8768 V 3.68 V 1.877 V 3.61 V Nearly the same 2.72 mA Decreases 1482 Ω
Difference of the recorded and measured R T Measure: R1 R2 Calculate: V1 V2 Measure: V1 V2
28 Ω
506 Ω 975 Ω 1.376 V 2.652 V 1.381 V 8.59 V
The calculated total voltage is almost the same as the measure total voltage, as shown in table 5, proving the claim of Georg Simon Ohm that voltage is directly proportional to the product of current and resistance. 6 CONCLUSIONS
In conclusion, if the circuit is connected in a series connection the voltage drop across each resistor are not the same but rather it is the sum of all voltage drop to obtain the total amount of voltage supplied. If the circuit is connected in a parallel connection the voltage drop across each resistor is the same as the voltage source. Another way in determining the value of resistance a resistor has was by using the color code. The measured total current was almost the same as the calculated total current also same thing happened in the calculated and measured total voltage using the Ohm’s law proving it valid.
REFERENCES
OpenStaxCollege. (n.d.). Retrieved from https://opentextbc.ca/physicstestbook2/chapter/r esistors-in-series-and-parallel/
