Ohm'S Law
Objectives:
The objective of this experiment is to authentication the Ohms Law and determine the resistance of resistors by applying Ohm’s Law.
Introduction:
German physicist George Ohm discovered the relationship between Voltage, Current, and Resistance in the electrical circuit. The current flowing through a fixed linearly connected resistance is directly proportional to the voltage applied across it and inversely proportional to the resistance at a constant temperature (Ohms Law). Using this ohm’s law an equation can be derived as follows. (V=voltage,I=current,R=resistance)
I(A) =V(v) R(Ω)
By knowing any two values of the Voltage, Current, or Resistance quantities unknown quantity value can be found using ohm’s law.
V = IR
I =V R
R =V I
According to this law, when the voltage applied across a constant resistance value increases, the current proportionally (𝑉 ∝ 𝐼). Conductors that adhere to this rule are called ohmic conductors. When plotting a graph by measuring various currents with changing voltage, ohmic conductors shows graph line like 𝑦= 𝑚𝑥. Conductors like these consider they are following ohm's law
Figure 01- Circuit Diagram
Materials:
- Ammeter
- Voltmeter
- Variabale
- DC Power supply
- 10Ω (±0.5)Resistor
- Wires
Procedure:
1. The circuit was set up as shown in figure 1.
2. When the current was too small, the range on the ammeter was adjusted to read accurately.
3. Starting voltage of the power supply was set to 0V and the voltage and current were read from the voltmeter and ammeter.
4. Supply voltage was changed for the 2, 4, 6, 8, 10, and 12 volts on the power supply.
5. All the current values and voltage values were read with respect to supply voltage change.
6. Using all the measured values, the graph was plotted.
7. According to the graph ohm's law was authenticated.
8. The resistance of the resistor was calculated by using the graph.
Observations and Results:
Table 01-Supply voltages, measured voltmeter, and Ammeter values
Graph 01 – Current vs voltage
Calculations:
𝑉 ∝ 𝐼
V=IR
y=mx
slop=m=R
m =8 0.7= 11.4
∴ R = 11.4Ω
Uncertainly Calculations:
Calculated R value =11.4Ω
Deviation = 11.4Ω - 10Ω = 1.4Ω
Tolerance = ±0.5Ω
Error = 1.4Ω - 0.5Ω = 0.9Ω
Conclusions:
This graph line shows y=mx, so this plotted graph authentications ohm’s law. According to ohm’s law, it’s satisfied under constant temperature value, but in here used 10Ω resistors for this experiment. According to observations, a large value of current flows through the resistor, that current value is a huge amount with respect to resistance value, so it causes to generate heat from the resistor. At the calculation, part resistance was calculated as 11.4Ω, but it should be 10Ω. The tolerance value of this resistor is±0.5Ω, According to calculation this resistor shows the deviation of 1.4Ω. After reducing the tolerance value it has a 0.9Ω error resistance value. That value has been generated by the heat of the resistor. This error can be reduced by increasing the value of the resistor. (~200Ω − 300Ω)
Discussion:
When doing a practical at the laboratory, errors occur under some conditions. Because they are not doing under absolute conditions and also elements are not ideal. So considering these issues errors can be correct by uncertain calculations. There are few observations noticed during the experiment.
As a first thing, there is some value difference between the supply voltage and voltage reading. There are two reasons for this issue, those are uncalculated resistance of wires and energy lost when heating resistor, but unfortunately practically unable to avoid from these issues. All the metal conducting wire has resistance and all the time heated elements lost their energy as heat. Only a slight correction can be made with an uncertain calculation.
References:
Experiment raw data source: https://www.scribd.com
Theoretical information source: https://www.wikipedia.org
0 Comments